I just shipped X1 to InFocus for the shrill noise problem, which began suddenly after about 1 year of fairly heavy use. It sounds like there is a power saw operating just outside my room.
It took several days for InFocus to issue an RMA after I reported the problem on their web site. They promise a turnaround time of 15 business days, so including shipping I'll be without the unit for about a month. And I had to pay shipping one-way to the service center.
It will be interesting to see if they fix the problem.
A footnote, I first believed --- naively, it seems -- that my extended warranty from the retailer, Circuit City, would cover the issue. But it seems that coverage only applies after the two-year manufacturer's warranty is over. I wonder what will happen if the problem recurs a year from now, expecially since the X1 is no longer manufactured. (I would not accept an X1a or X2 as a replacement.)