Someone could have gave you a solution already, but I have one
I don't get that, but I do get this ALL the time. The only way I can get around it is to go into IE properties, delete all cookies and then delete all off line content. This is not a problem with this site however as I do not get this error at home. So, my question would be do you get your error regardless of what computer your are on?
If you get firefox you can set the properties to clear cookies, ect. when it closes. That could help what you have. Also it does it much faster (very fast) and doesn't cause firefox to "lock" up like IE6. Hope that helps.