Stop background find in “visual studio” not always stops search

In VS 2005 (I have SP1) it is a toolbar icon called “Stops a background Find”, that suppose to cancel the find .

However I noticed on my machine and on my colleage’s machine, that sometimes VS hangs on searching(shows the search as processing, but doesn’t change the filename on status bar).The button nether shortcut (Alt-F3,S)  doesn’t stop search and you need to close VS to re-enable searching.
I don’t have enough details to reproduce the problem, so it is pointless to report to MS Feedback site