I restarted my zen server the week because I noticed some general slowness and many of the 100 or so computers I have running the agent were constantly getting the Zen login window each time a user logged in.

After restarting the system is running quickly again. Now however, every single machine in the system is asking for the second zen login and complains about the server certificate being incorrect.

The exact wording is:
Unable to log into the network because the login credentials or the server certificate is incorrect.

Until this week everything has been running smoothly. All machines were authenticating the users the first time around without slowing anything down. My login speeds have actually been very fast lately.

*Nothing on my network has changed.
*Running the latest updates and PRU.
*All windows environment.
*All machines are XP pro SP2 or SP3 (most are SP3)

Does anyone have a clue why this would suddenly happen?