Page 1 of SONY VPL overheating - please help !!!

hi i have a sony VPL-CSI.
About 3 years old, one of those ones which were on special from PC world.
The problem is, after 2 or 2.5 hours of use it shuts off. The temp / fan light flashes.
The instructions say that means it needs to be repaired, because the fan is broken. But I`m not sure how that could be - If it`s broken how can it work fine for 2 hours + ?
I phoned Sony prime support, who said I should take the filter out and clean it in warm water, before drying throughly and replacing. Also run a hoover lightly over all vents.
Basically get rid of dust.
Will this work ? Or might there be a problem with the fans ?
all the vents are at least an 2 inches away from walls etc. Although it usually rests on books, maybe the underside vents aren`t getting enough air...
Any ideas ? This problem is really beginning to annoy me...I`ve used it for about 100 hours.
This problem occurred after about 40 hours...
Thanks!

If Sony support think it will work, then give it a shot, some hel(l)pdesks do actually have a clue. You have nothing to be lost by trying.