One fine day, all of a sudden, my Visual Studio 2008 IDE started throwing up this error message in the "Output" window when I was using "Find and Replace Dialog" -> "Find in Files" -> "Entire Solution" feature:
"No files were found to look in. Find was stopped in progress."
To resolve this issue, press Ctrl+Scroll lock and then run the search again. This solved the problem.
You could also try Ctrl+Break.
See MSDN: http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=105511
This nasty bug has also been reported in Visual Studio 2005 (VS2005).