Out of sync with server error when URL gets too long

We are having an issue when a user (not Administrator) logs into MWS and picks up a task from their inbox. They then click back to their inbox (via a link in the left nav) and pick up a task again, we then get an error message that the state of the page may be out of sync with the server and the page becomes unresponsive.

Has anyone else experienced similar issues?

Out of curiosity, is this the standard inbox or a custom inbox? If it is a custom inbox, did you modify the URL created from the command link?