Sorry, but the problem is with the software. It needs to provide a clear error message to tell me what to fix.
If I knew what the problem was, I would do something about it. However, at this point the only thing I can do is try to debug a piece of software that I'm not familiar with, which is not easy to do.
Earlier, somebody mentioned that adding a single PHP constant to a file fixed the problem. Is that working for you? If not, does it help if you wait until the server is under less load (~4)?