Hi, in summary: I'm having the same problem.
A little more detail: I also got the x on the release date, and it was great over the weekend. Then I decided that it was time to get music working, which was kind of a nightmare. Doubletwist works almost as poorly as WMP for me, and it was being used at the start of my troubles:
I was syncing with doubleTwist, but it took hours and it was time to head out, so I clicked the cancel button, and after syncing stopped, turned off the computer. I then unplugged the phone. On the way home, I kept hearing it restart.. over, and over, and over again. Since then, it has been restarting every few minutes UNLESS it is plugged into the computer via USB. Then it functions perfectly normally. Yesterday it became frozen on the Motorola start screen, which I noticed when the screen started to heat up dramatically. I had to pull the battery. I've done a system restart as well, no luck. I've also removed doubleTwist (it actually always says sync fails.. and as an aside, the only way I was able to get music working and ordered by Track#, not alphabetically, was to select USB mode "USB mass storage" and drag and drop music folders into the Music directory. I hope that helps someone), and advanced task killer (which would auto start every time the thing crashed before), still no luck.
Anybody try anything else? I'm concerned that if I get a replacement, it will simply do the same thing in a few months, or maybe when my warranty runs out.
"Should i consider taking it back to the store to get a replacement?" -rboutin2
I tried this, and was told by a useless employee that they're expecting a shipment next week, but no offer to put one aside for me. I contacted the salesman who I bought it from, and am awaiting reply. Either that, ship it out and wait for a new one to come in, or get an iphone 4.