Hi,

I am using Umbraco Version 4.0.4.2, Asp.NET: 2.0.50727 on Windows Server 2003 Enterprise  SP 2, IIS 6.

I notice that in umbraco Concierge, this error occurrs every couple minutes:

Error loading IApplication: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.IO.FileNotFoundException: Could not load file or assembly 'umbraco.dll' or one of its dependencies. The system cannot find the file specified.
File name: 'umbraco.dll'
at System.Reflection.Assembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)
at System.Reflection.Assembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)
at System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
at System.Reflection.Assembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
at System.Reflection.Assembly.Load(String assemblyString)
at Umbraco.Concierge.Businesslogic.application..ctor()

WRN: Assembly binding logging is turned OFF.
To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1.
Note: There is some performance penalty associated with assembly bind failure logging.
To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog].

--- End of inner exception stack trace ---
at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandle& ctor, Boolean& bNeedSecurityCheck)
at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean fillCache)
at System.RuntimeType.CreateInstanceImpl(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean fillCache)
at System.Activator.CreateInstance(Type type, Boolean nonPublic)
at System.Activator.CreateInstance(Type type)
at umbraco.BusinessLogic.Application.RegisterIApplications() in d:\TeamCity\buildAgent\work\7380c184e9fcd3ea\umbraco\businesslogic\Application.cs:line 228

I would like to troubleshoot this frequent error further, but am not sure where to start.

I've looked at the registery suggestion to turn binding logging on, but that setting is not there in the registry. I've read that I need to install Windows SDK in order to use the Fusion tool. I installed .NET Framework 2.0 SDK (x86) and was able to run the Fusion Assembly Binding Log Viewer.

I rechecked the umbracoLog (and concierge) to find that my log entries now have pre-bind state info:

Error loading IApplication: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.IO.FileNotFoundException: Could not load file or assembly 'umbraco.dll' or one of its dependencies. The system cannot find the file specified.
File name: 'umbraco.dll'
at System.Reflection.Assembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)
at System.Reflection.Assembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection)
at System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
at System.Reflection.Assembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection)
at System.Reflection.Assembly.Load(String assemblyString)
at Umbraco.Concierge.Businesslogic.application..ctor()

=== Pre-bind state information ===
LOG: User = WEB1\UCPR
LOG: DisplayName = umbraco.dll
(Partial)
LOG: Appbase = file:///C:/Inetpub/wwwroot/capradio/
LOG: Initial PrivatePath = C:\Inetpub\wwwroot\capradio\bin
Calling assembly : Umbraco.Concierge, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null.
===
LOG: This bind starts in default load context.
LOG: Using application configuration file: C:\Inetpub\wwwroot\capradio\web.config
LOG: Using host configuration file: \\?\C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\aspnet.config
LOG: Using machine configuration file from c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\config\machine.config.
LOG: Policy not being applied to reference at this time (private, custom, partial, or location-based assembly bind).
LOG: Attempting download of new URL file:///c:/WINDOWS/Microsoft.NET/Framework/v2.0.50727/Temporary ASP.NET Files/root/2b3a7d95/28e12640/umbraco.dll.DLL.
LOG: Attempting download of new URL file:///c:/WINDOWS/Microsoft.NET/Framework/v2.0.50727/Temporary ASP.NET Files/root/2b3a7d95/28e12640/umbraco.dll/umbraco.dll.DLL.
LOG: Attempting download of new URL file:///C:/Inetpub/wwwroot/capradio/bin/umbraco.dll.DLL.
LOG: Attempting download of new URL file:///C:/Inetpub/wwwroot/capradio/bin/umbraco.dll/umbraco.dll.DLL.
LOG: Attempting download of new URL file:///c:/WINDOWS/Microsoft.NET/Framework/v2.0.50727/Temporary ASP.NET Files/root/2b3a7d95/28e12640/umbraco.dll.EXE.
LOG: Attempting download of new URL file:///c:/WINDOWS/Microsoft.NET/Framework/v2.0.50727/Temporary ASP.NET Files/root/2b3a7d95/28e12640/umbraco.dll/umbraco.dll.EXE.
LOG: Attempting download of new URL file:///C:/Inetpub/wwwroot/capradio/bin/umbraco.dll.EXE.
LOG: Attempting download of new URL file:///C:/Inetpub/wwwroot/capradio/bin/umbraco.dll/umbraco.dll.EXE.

--- End of inner exception stack trace ---
at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandle& ctor, Boolean& bNeedSecurityCheck)
at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean fillCache)
at System.RuntimeType.CreateInstanceImpl(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean fillCache)
at System.Activator.CreateInstance(Type type, Boolean nonPublic)
at System.Activator.CreateInstance(Type type)
at umbraco.BusinessLogic.Application.RegisterIApplications() in d:\TeamCity\buildAgent\work\7380c184e9fcd3ea\umbraco\businesslogic\Application.cs:line 228

Again I'm concerned because this error is occurring every couple of minutes. From time to time this website creeps to stand still (hanging), even on a 4 cpu system. I'm really just trying to start from the ground up and understand all the errors so I can figure out what needs to be done. 

The only thing I can think of is of a usercontrol that I recompiled at the end of December and the datestamp on two .dll's used by that control (called playlist.dll and playlist.pdb) files changed. So I pushed the updated .dll out to the bin folder of the production website . But umbraco .dll is not one of the files touched by that recompile. I have not done any other work that I think would cause an umbraco.dll dependency error. Also, I am puzzled by the pre-bind log entries that are looking for this umbraco.dll file. what is this "new URL file" message?

Any help appreciated.