After completing an in-place upgrade Excel Services was unable to open workbooks in the browser. I was confident I had everything configured properly.
When trying to open a workbook in the browser I got the nondescript Error – Workbook cannot be opened. There was nothing in the server application log and the SP logs didn’t offer much insight.
Restarting IIS, rebooting the server, changing the service accounts and modifying the database permissions didn’t solve what seemed to be a simple problem.
I turns out that my Front End servers had a different version of Excel Services than the Application Server that was actually running the service. I have no idea how they got out of sync.
Installing Service Pack 1 and running PSConfig quickly resolved the issue.
SP1 installed with no problems. I’ve heard that the June CU has created problems for some folks especially the User Profile Synchronization service. I’m electing not to install the June CU until later.