Why would our program suddenly get password certification errors and then later stop getting them?

I work as a programmer, but I have only sketchy knowledge of what goes on with the communication functions. To me they are just black boxes that send data provided everything is okay. We were required to get password certification through a company called DataPower, which is affiliated with IBM.

Our program ordinarily works fine, but yesterday, in the process of calling a client’s Web service functions, we were getting socket errors. Our LAN team looked into the data streams back and forth and found that the specific error was rejection of password certification. Nobody had a clue as to what the cause was, but in the process of periodically restarting the program to see what was going on, the errors eventually stopped and the program is now running.

Any computer experts here have any idea of what might have been going on?