Novell 5 inaccessible

I dont know much about Novell, except how to connect to it. I have a Novell 5 server that will, overnight, quit accepting requests. The next morning, the Windows XP boxes, with the latest Novell client will not be able to connect to the server just as if it was not on. Are there any event logs or anything like that to check for errors?? Any ideas would be greatly appreciated.

TIA