[HttpWebRequest_WebException_RemoteServer] Arguments not found in a SilverLight app. Event log suggests app pool recycling issue but timeouts set to 0

Displayed_Errors.txtHi,

I'm seeing this message:

"[HttpWebRequest_WebException_RemoteServer] Arguments not found" in a SilverLight app. Further details relating to Application Pool recycling appear in the event log

WebHost failed to process a request.
Sender Information: System.ServiceModel.ServiceHostingEnvironment+HostingManager/4810345
Exception: System.ServiceModel.ServiceActivationException: Request to the service at '~/Services/WebAppSystemService.svc' cannot be dispatched because the virtual application at '/IDCLauncher' is shutting down. ---> System.InvalidOperationException: Request to the service at '~/Services/WebAppSystemService.svc' cannot be dispatched because the virtual application at '/IDCLauncher' is shutting down.
   --- End of inner exception stack trace ---
   at System.ServiceModel.ServiceHostingEnvironment.HostingManager.FailActivationIfRecyling(String normalizedVirtualPath)
   at System.ServiceModel.ServiceHostingEnvironment.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath, EventTraceActivity eventTraceActivity)
   at System.ServiceModel.ServiceHostingEnvironment.EnsureServiceAvailableFast(String relativeVirtualPath, EventTraceActivity eventTraceActivity)
Process Name: w3wp
Process ID: 3064

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Attached error log entry indicates apps pool recycling issue. Have changed timeouts to 0 in the relevant pool and after restart no joy. The SilverLight app, amongst other things, launches correctly but fails when user credentials are entered which we know is the point at which it tries to contact our separate database server on the same domain.

Used to work well but had this problem of late and not clear anything has changed. Running Windows 2008 R2 server. Latest SilverLight installed too.

All & any help gratefully recieved!

Thanks in advance
Iain