Unexpected state Error for task task name

You can encounter this error when the science application has somehow become corrupted. It's also possible that BOINC does not have the right permissions to do read/write operations in its data directory.

Corruption can be solved by detaching from the project and reattaching (this deletes everything in the project's folder and downloads all necessary items anew); Permission trouble can only be solved by uninstalling and reinstalling BOINC.