The background:

We've been working on a client site on a dev server using 4.0.2.1 for several months. Earlier this week, we moved the site to a production server and after a few hiccups have been up and running ever since. So far, the only problem is that the sections of the site that are protected with "Public Access" have been returning the "Server Error in '/' Application" error both when I try to access them with the correct username and password and when I try to edit their access through the admin. I haven't been able to duplicate this on the dev server. I've compared the web.config files and the only differences are the umbracoDbDSN keys, as they should be.All other areas can be edited successfully.

I appreciate any help or insight that anyone may be able to give. My team is stumped.

My login template is identical on the 2 servers:

   <div class="loginCenter">
            <form runat="server">
  <asp:LoginView ID="LoginView1" runat="server">
      <LoggedInTemplate>
                Welcome
                <asp:LoginName ID="LoginName1" runat="server" />
                <br />
                <a href="#">Continue...</a>
            </LoggedInTemplate>
            <AnonymousTemplate>
        <h2>Log In</h2>
                <asp:Login ID="Login1" runat="server">
                    <LayoutTemplate>
                      <asp:Label ID="UserNameLabel" runat="server" AssociatedControlID="UserName" class="block">User Name:</asp:Label>
                      <asp:TextBox ID="UserName" runat="server" class="text"></asp:TextBox>
                      <asp:RequiredFieldValidator ID="UserNameRequired" runat="server" ControlToValidate="UserName" ErrorMessage="User Name is required." ToolTip="User Name is required." ValidationGroup="ctl00$Login1">*</asp:RequiredFieldValidator>
<br /><br /><br />
                      <asp:Label ID="PasswordLabel" runat="server" AssociatedControlID="Password" class="block">Password:</asp:Label>
                      <asp:TextBox ID="Password" runat="server" TextMode="Password" class="text"></asp:TextBox>
                      <asp:RequiredFieldValidator ID="PasswordRequired" runat="server" ControlToValidate="Password" ErrorMessage="Password is required." ToolTip="Password is required." ValidationGroup="ctl00$Login1">*</asp:RequiredFieldValidator>
                      <br />
              <asp:CheckBox ID="RememberMe" runat="server" Text=" Remember Me" /><br /><br />
                      <asp:Button ID="LoginButton" runat="server" CommandName="Login" Text="Log In" ValidationGroup="ctl00$Login1" />
                      <br />
                      <asp:Literal ID="FailureText" runat="server" EnableViewState="False"></asp:Literal>
                                      </LayoutTemplate>
                </asp:Login>
            </AnonymousTemplate>
        </asp:LoginView>
            </form>
 </div><!-- end loginCenter -->

And here is the error that I'm getting. I get this both when I attempt to access the protected sections of the front end as well as when I attempt click  "Public Access" on the backend on the already protected sections.

Server Error in '/' Application.
         
 A network-related or instance-specific error occurred while establishing
a connection to SQL Server. The server was not found or was not
accessible. Verify that the instance name is correct and that SQL
Server is configured to allow remote connections. (provider: SQL
Network Interfaces, error: 26 - Error Locating Server/Instance
Specified)          

             Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the
error and where it originated in the code. 

             Exception Details: System.Data.SqlClient.SqlException:
A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or
was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL
Network Interfaces, error: 26 - Error Locating Server/Instance Specified)



            Source Error: 
            

               

                  

                      
An unhandled exception was generated during the execution of the
current web request. Information regarding the origin and location of
the exception can be identified using the exception stack trace below.

                  
               
            


         


            Stack Trace: 



            

               

                  

                      
[SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified)]
   System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +4846887
   System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +194
   System.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Boolean encrypt, Boolean trustServerCert, Boolean integratedSecurity, SqlConnection owningObject) +4860189
   System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject) +90
   System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart) +376
   System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance) +221
   System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance) +189
   System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection) +4861315
   System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options) +31
   System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject) +433
   System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject) +66
   System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) +499
   System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +65
   System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +117
   System.Data.SqlClient.SqlConnection.Open() +122
   System.Web.DataAccess.SqlConnectionHolder.Open(HttpContext context, Boolean revertImpersonate) +87
   System.Web.DataAccess.SqlConnectionHelper.GetConnection(String connectionString, Boolean revertImpersonation) +221
   System.Web.Security.SqlRoleProvider.GetRolesForUser(String username) +760
   System.Web.Security.RolePrincipal.GetRoles() +158
   System.Web.Security.Roles.GetRolesForUser(String username) +365
   System.Web.Security.Roles.GetRolesForUser() +14
   umbraco.cms.businesslogic.web.Access.HasAccces(Int32 documentId, Object memberId) +96
   umbraco.requestHandler..ctor(XmlDocument _umbracoContent, String url) +3762
   umbraco.UmbracoDefault.Page_PreInit(Object sender, EventArgs e) +903
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
   System.EventHandler.Invoke(Object sender, EventArgs e) +0
   System.Web.UI.Page.OnPreInit(EventArgs e) +8698174
   System.Web.UI.Page.PerformPreInit() +31
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +282