I've checked the other threads relating to this message, and they all seem to occur when the user goes into IE. However, this happens on my work PC every time we boot it up. The message is:
Server Busy This action cannot be completed because the other program is busy. Choose 'Switch To' to activate the busy program and correct the problem.
Options are: Switch To..../Retry/Cancel
Cancel is greyed out. If you select either of the other two, the message disappears then comes back a few seconds later. If you keep pressing retry enough times, the message will go eventually but anyway it does disappear of its own accord after a while - may be a couple of minutes, may be longer. Doesn't seem to affect anything - don't have any spyware pop-ups or anything like that.