Bought my One X + a little over a week ago, and have had the same issues. Randomly no signal with the SIM card icon with exclamation point next to it. After rebooting it fixes it, but still happens at least once a day. I'm guessing it's bad contacts between the gold contact points. I've read elsewhere you can shim by layering scotch tape on top of SIM card (opposite side of gold contacts) and that helps it have a better contact with contacts in the phone, however I haven't done this and don't plan on it because i'd rather not screw something up. If customer support cannot help, I'll try to wait it out until the company or someone else comes up with a better fix. still glad i jumped off the iphone bandwagon for this though!