SharePoint 2010 has a new feature which recycles the OWSTIMER.EXE process every night – similar to the application pool functionality in IIS – to avoid memory problems inside the timer service.
The recycling is controlled by a new timer job which has been added in SharePoint 2010: the "Timer Service Recycle" job which per default runs once a day at 6 AM.
While performing the recycling and shutting down the timer service the timer service runs into a problem in .NET which Tess Ferrandez has explained here.
The problem here is that the encryption key was created on a specific thread which was impersonated under a specific users account. When the .NET Finalizer processes the encryption key while the timer service shuts down it executed on a different thread which is not impersonated - so the key does not exist and you get an exception like "keyset does not exist".
As this exception occurs in the final stages of the shutdown of the process it does not cause any harm – beside adding an event to the event log when it happens:
An unhandled exception occurred and the process was terminated.
Application ID: DefaultDomain
Process ID: 4213
Message: Keyset does not exist
StackTrace: at System.Security.Cryptography.CryptographicException.ThrowCryptogaphicException(Int32 hr)
at System.Security.Cryptography.SafeProvHandle._FreeCSP(IntPtr pProvCtx)
at System.Runtime.InteropServices.SafeHandle.Dispose(Boolean disposing)
A more visible problem for a customer will occur when Visual Studio or a another JIT Debugger is installed on the affected box. In this case the following dialog will show up on the Console when the problem occurs:
Uninstalling Visual Studio will not resolve this issue as the registry settings which present this dialog are still active.
To configure the server to no longer show a dialog when an unhandled exception occurs, use the registry editor to delete the following registry keys:
- HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug\Debugger
On a 64-bit operating system also delete the following registry keys:
- HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug\Debugger
More details are at: