StaffordCabling

One more thing to try is to run the VGA through a splitter, as the built in amp sometimes helps with this and I'm sure you have one around to try as a test. We have some sites where this is an issue even when both are plugged into the same socket. Usually a different lead can sort it but if it's 25m long that could be a pain. Try the laptop plugged in via a small 2m lead and see if it does the same thing. One last suggestion if all else fails is to see if you can swap the projector for one in another room, as some models are worse than others for this.

It should show a lamp error if it was the lamp, if it's not overheating it could be a fan cutting out or the temp sensor gone faulty. NEC are really good with replacements and may even send one ahead for you. If you can find out who the reseller is try through them, I know most of the NECs we've supplied have a 3 year swap out warranty for education so even without the original invoice they might be able to help.

Have you tried using some strong tape on the surface to pull the outer skin away from the inner? Sometimes in high use areas of the board after a few years they will remain too close to each other and mess up the orientation. If all else fails try some gaffa tap to pull different areas off the inner skin then give the board a thorough clean and try again.