Troublesome Dell 3300MP projector

I am working at the University of Oslo and we (the Chemistry Institute) are using a Dell 3300MP projector in one of the auditoiums. This projector does not start using the remote control (RC). I have to switch it on using the "manual" button on the projector itself. But after that, the RC works just fine. I have talked a lot to my Dell-support, but they can not solve this problem. Here is a short resume ; I always check the projector at arrival (connect the power cord and trying the RC) - everything works ok. Then I mount this projector upside-down in the roof, connect the DVI-cable and power cord, but now I can not start my projector. I disconnect the DVI and it starts (I am using the RC all the time, when the projector is switched on I also use the RC to turn it off. As long as the projector is on, the RC works just fine!). I connect the cable again and it suddenly works again. Then I tightened the screws for the DVI-connection, but now nothing happens. I then disconnect and reconnect the DVI, tighten the screws and now it starts. This was late in the evening, so next morning I try it again, but no - nothing happens! I change the USB-connection (you should know that this DVI-cable also has an USB-connection built in, so that it possible to use the RC as a mouse regarding the pc), the USB-function reinstalls on the pc and again the projector starts normally. The next morning the projector is dead again. I undo my USB-connection from previous day and it starts again. To be sure I try once more, but this time nothing happens. Then I disconnect this USB-function (and leaving it unplugged) and the projector starts. And it also started the next time, when a professor had his lesson. I will leave it like this for a while and see what happens next (or for how long it will work).

So my question is simply, since I don't understand what is going on, anybody who knows or have experienced the same problem? We have several other projectors, both Dell and non-Dell, also with this USB-function, and they all work just fine. So why not this particulary projector (3300MP) ?

Thanks for any answer.