I'm probably totally wrong since no one else seems to have suggested it, but wouldn't the belt slacken with a broken rocker anyway?
I mean, if you don't have the valves, rockers etc in contact with each other properly (which you don't, since it's broken) then the cams will move round a tad, thus loosening the belt.
The way to tell is if the timing marks still line up or not when you turn everything into alignment.
I would have thought this was a symptom rather than a cause, because if the belt was fitted wrong, or too loose from fitment I would have thought it would have gone sooner.
Like I said though, I might be barking up entirely the wrong tree!
[Edited on 23-6-2005 by desmojen]
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