ERROR: request not found in the TrackedRequests. We might be creating and closing webs on different threads.

Answer 1

We had the same problem and found a possible solution.

Although we were disposing our SPSite and SPWeb objects properly, we forgot to dispose the BinaryStream we took of the SPFile object.

We are still seeing the same problem on SharePoint Designer workflows, even when they contain no actions. I have started a separate thread for that issue.