I have a fantastic HTC 8x Windows phone, but it has a couple of infuriating hardware problems. The phone randomly displays "SIM Error The SIM card is missing or invalid. You can still make emergency calls if your mobile operator supports it."
The internet tells me this is a common problem on these. That sucks. Today will be the magic day when I get off my lazy duff and ask them for a replacement.
Follow-up: Not bad, 10 minutes on the live chat and they'll send me a new SIM tray. Ok, that's a little annoying as I asked for a new SIM tray two months ago and they told me to get a new SIM card from AT&T first. :/
Follow-up 20140423: The new SIM tray fixed it! Now I have to figure out why it powers off when the Battery hits 22%.