Windows Server 2008 R2 (Hyper-V VM)
SharePoint Server 2010
Running IE8, FireFox, SharePoint Designer 2010
"This action cannot be completed because the other program is busy. Choose Switch To to activate the busy program and correct the problem."
I haven't totaly figured out what's happenning here. The only thing that solves it is restarting the server.
I do think my issue is due to low memory available, and when the IIS is constantly asking for more memory than what is available in the system, eventually I get this error. So while working on the server, regular iisresets keeps this from happening.