Windows Service exposing WCF: most EventLog entries not appearing in the event-log?

I have some very odd situation at a client that wants me to maintain some of their software:

upon start/stop, the EventLog entries of a Windows Service are correctly appearing.

But during incoming WCF calls, they are not.

All EventLog crea开发者_Go百科ting is going through the same global static factory class.

When I put all classes in a console app, everything logs fine.

When sending those entiries to OutputDebugString, the same happens: windows Service Startup/Shutdown are coming through fine, but WCF execution not.

Where should I start digging?

These kinds of problems are hard to figure out. I would start by attaching the debugger to the WCF service and adding some breakpoints in the logging classes and see if the code actually stops. If not move the brake point to the service and see why it doesn't get into the logging code.

Given that the code works in a console app and only partly in a WCF service my first guess is that it could be a threading issue. But without more info that is just pure speculation.