I once worked for a company that had a product that caused OTHER applications to crash.
We didn't believe it at first. People would call our support line and complain that other apps would crash while using our product. But the crash was not reproducible, and the whole thing seemed kind of silly anyway. If another app crashed while ours happened to be running, how could it be our fault?
It turns out they were right. This was on a Mac, before the OS X days. One of our dialog boxes was failing to release a handle to a palette resource. And strangely enough, this had the effect of sometimes causing other applications to fail.
-- Eric Sink
Do you have a bug whose story you love to tell? Let me know!