Downgrade to 3.0.14 for the moment, will look into the error next week

How, exactly do I downgrade? 

I have the same problem with the same version of umbraco, and the problem presists after doing the downgrade.

I assume that to downgrade i simply download version 3.0.14 and extract its files to the root level of my site, overwriting the existing contour files.

stack trace:

[MissingMethodException: Method not found: 'umbraco.DataLayer.ISqlHelper umbraco.DataLayer.DataLayerHelper.CreateSqlHelper(System.String, Boolean)'.]
   Umbraco.Forms.Data.Helper.Connect(String connection) +0
   Umbraco.Forms.Data.Storage.FormStorage..ctor() +50
   Umbraco.Forms.UI.Dashboard.FormsDashboard.Page_Load(Object sender, EventArgs e) +1435
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +25
   System.Web.UI.Control.LoadRecursive() +71
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Control.LoadRecursive() +190
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3064

Yeah just follow the same steps as you would on upgrade http://our.umbraco.org/projects/umbraco-pro/contour/documentation/Installation/Upgrade

Thanks for you reply Tim,

I have followed the steps in the upgrade guide but the page at [My site]/umbraco/plugins/umbracocontour/upgrade.aspx
Gives me the following error:

[MissingMethodException: Method not found: 'umbraco.DataLayer.ISqlHelper umbraco.DataLayer.DataLayerHelper.CreateSqlHelper(System.String, Boolean)'.]
   Umbraco.Forms.Data.Helper.Connect(String connection) +0
   Umbraco.Forms.Data.Storage.FieldConditionStorage..ctor() +26
   Umbraco.Forms.UI.Pages.Upgrade.Page_Load(Object sender, EventArgs e) +122
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +25
   System.Web.UI.Control.LoadRecursive() +71 

System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3064 

3.0.15 game me the same error on the update page, and i therefore had the server guy run the manual SQL update script on the database, so that should also be in order unless there are database differences between .15 and .14

I was able to make 3.0.14 work finally by uninstalling .15 and re-installing 3.0.14. The install does not really completely install, so 1) run the install, (this will crash your entire website however with a YSOD) so you then need to manually remove the DLL's that dont' get removed by the uninstall (Umbraco.Forms.*****), then clean your webconfig by stripping out the assembly references that also don't get removed from the uninstall. Then install 3.0.14...

I tried doing as Jamie suggested but now i have no contour icon on the dashboard and the content page referances a missing  '/usercontrols/dashboards/ContactForm_logs.ascx'. 

Not even sure where this came from since i do not have the file anywhere, neither in my backup of the old site or in any of the new manual installs.

Installation guide tells me to insert them though, and i followed it step for step...

visiting the upgrade link now gives me this error:

[SqlException (0x80131904): Foreign key 'FK_UFFieldConditions_UFFields' references invalid table 'UFFields'.
Could not create constraint. See previous errors.]
   System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) +404
   System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning() +412
   System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) +1363
   System.Data.SqlClient.SqlCommand.RunExecuteNonQueryTds(String methodName, Boolean async) +2899708
   System.Data.SqlClient.SqlCommand.InternalExecuteNonQuery(DbAsyncResult result, String methodName, Boolean sendToPipe) +504
   System.Data.SqlClient.SqlCommand.ExecuteNonQuery() +327
   Microsoft.ApplicationBlocks.Data.SqlHelper.ExecuteNonQuery(String connectionString, CommandType commandType, String commandText, SqlParameter[] commandParameters) +167
   umbraco.DataLayer.SqlHelper`1.ExecuteNonQuery(String commandText, IParameter[] parameters) +171

[SqlHelperException: Umbraco Exception (DataLayer): SQL helper exception in ExecuteNonQuery]
   umbraco.DataLayer.SqlHelper`1.ExecuteNonQuery(String commandText, IParameter[] parameters) +371
   Umbraco.Forms.UI.Pages.Upgrade.Page_Load(Object sender, EventArgs e) +1498
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +25
   System.Web.UI.Control.LoadRecursive() +71
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3064

I encountered the same error when trying to upgrade from Contour v1.x to Contour v3.0.15 on an Umbraco v4.7.0 installation...

Method not found: 'umbraco.DataLayer.ISqlHelper umbraco.DataLayer.DataLayerHelper.CreateSqlHelper(System.String, Boolean)'.

I then uninstalled the Contour v1.x package through the Umbraco Repository and performed a fresh install of Contour, again through the Umbraco Respository (v3.0.15?), and received the same error.

The good news is that extracting UmbracoContour_3.0.14_update.zip per Tim's instructions above seems to have corrected the issue.

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