did you try to pry off the screen like the example someone posted in the forums. I had the same problemo and I pryed the screen wiped it clean bought an Otterbox and have not thought about it since. Issue solved.
I guess when I think about it, if you have the put the phone in a "dusty" place you will have dust in the phone, no matter how many times the phone gets replaced. Yes the design could have been better, but I would try a case or something of that nature.
