Unknown Project Server Error

Hello! I am very skilled with Project Server, but I have run across an error that I have never seen before. The error occurs through PWA when a user is trying to accept time for multiple tasks. The error simply says: unknown error.

The only work around we have been able to find is to accept time for one task at a time. We have restarted the servers and back end services to no avail.

Has anyone seen this error before? Does anyone know how to fix it?