Visual Studio Find occasionally stops working

I got into work this morning to discover that Find had stopped working in Visual Studio.  Instead of returning the correct matches it returns a particularly unhelpful message: “Find was stopped in progress.” I recall coming across this issue in VS2003 but thought that it had been fixed in VS2005.  A quick trawl returned a couple of options, the one that fixed my solution was pressing Ctrl-ScrLk. Don’t know exactly what this key combination is supposed to do (and to be honest haven’t bothered to look it up) but it does seem to cancel an executing Find.  For some reason VS occasionally seems to get stuck thinking that it should always cancel any Find.  Pressing this key combination resets this flag allowing you to resume searching.