Root cause of bug 594635. The problem was fixed by using a nsITimer. The timer was firing using an internal of 500ms but using an interval < 100ms the timer was not firing. I tracked this down to MessageLoop::PostTask_Helper where the correct interval is passed yet the timer never fires. Even if nothing is affected (since bug 594635 worked around the issue) it may be worth exploring as it may cause future issues.
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