This is definitely in the category "I-would-believe-it-if-I-would-see-it-with-my-own-eyes".
Coworker tried to "search in files" in Visual Studio 2005 and he got zero results. Even when he searched for simple "a" character, he still got nothing. Then we noticed the message in results pane:
No files were found to look in. Find was stopped in progress.
He googled it and fairly quickly found a solution on Franny's Adobe blog.
Pressing Ctrl + Scroll Lock actually helped! It's important to mention the above solution and error was spotted in Visual Studio 2003 but coworker had same thing in 2005.
It looks like somehow "Break" command which is Ctrl + C or Ctrl + Pause got stuck. But that has nothing to do with "Scroll Lock". Go figure. Weird, weird, weird... How the hell would anyone solve this without internet?!? Thank you, Tim, thank you!