"Server Busy" circular error.

I get a "Server Busy" error message every time I open OP-17. The messgae tells me that another application is using the connection, Click Retry or switch to the other application and clear it.

I click the retry button again and again to no avail. Clicking the switch to button simply opens the XP start menu and gives me no idea of what server is busy and what program is doing it!