Problem: I have a brand new SharePoint Server 2010 farm, only a few months old and up until today my Excel Services was working flawlessly. Today, however, I noticed that my dashboard pages were all displaying error messages in my Excel Access web parts. All of them displayed the pop-up error box with the message: “Unable to process the request. Wait a few minutes and try performing this operation again.”
Solution: I did an IIS Reset on my WFE and my Apps servers, and it magically fixed everything.