I saw this error on a Windows XP box recently when I went to change an IP address – the message continued to tell me that another properties dialogue open, and that I should close that. I couldn’t find another dialogue of any kind opened, ro I rebooted teh PC. Same problem. A colleague (thanks Laurie B) knew how to fix it.
Go to Task Manager (CTRL+ALT+DEL will get you there)
Go to the Processes Tab
Sort by CPU – so max CPU is at the top
Look for the svchost.exe process that is using the most CPU