Well, if the computers are networked, it would seem to follow that firewall settings could change. Try this:

• Close all other windows and browser tabs on your computer except this one.
  
• Click this logout link
  
• Logout a second time to clear all traces of Mudcat cookies.
  
• Click this login link and log in.

I don't know if this will work because your situation is a bit unusual, but it's worth a try.
-Joe-