Usually this is due to the proxies used and the various steps of authentication required. Some Javascript scripts don't handle the IP changes well and wind up throwing this error.

The easiest fix would be to use a different browser. Have you tried Firefox or Chrome? They both handle script errors better. Chrome in particular.

Alternately, completely killing internet explorer should stop the errors when they're happening. Hit ctrl-alt-delete and click "task manager." From there, you want to click the header above all the .exe names to sort by name. Find any listing of iexplore.exe and click it to kill the process.