MacBook Air - upgraded HD, now does not boot up

Upgraded my hard drive from a 250gb to a 500gb. After reinstalling Mountain Lion, I did a restore from my TM backup. All seemed to go well, and was quick.

The system told me to reboot after the install and again all was good, but it won’t complete the boot. Apple symbol comes up, progress bar starts up, slows down, then stops. I am looking at a screen that is ready to start the GUI, but... it just sits. I tried restarting, no different.

Any ideas?

You can try starting in Safe Mode. Restart your Mac and immediately after your Mac starts (some Mac computers play a startup sound), press and hold the Shift key. Release the Shift key when you see the progress indicator. See if this works. If so edit your question mentioning that it works in safe mode, and leave a comment here.