We just upgraded to WCF 4 on IIS 6 (running in WoW 32 bit mode), and all of a sudden the services started running into what appears to be concurrency problems.

Upon finding out we had a problem, we changed the Behavior Configuration Changes on the WCF server to the follow:

<serviceThrottling
             maxConcurrentCalls="1000"
              maxConcurrentInstances="1000"
              maxConcurrentSessions="1000"
            />

We also changed the number of worker processes from 1 to 5. Doing all of this seemed to have no effect. The service seemed to be running, but throttled by something. Is there anything else that might need to be changed to remove the "artificial" throttling?

Were using the default configuration WCF which should be Per-Call (not singleton).