I had similar problems. Windows 7 boot hanged on welcome screen. Finally i pin-pointed the problem to avast. First i disabled avast start-up in safe mode. After that Windows booted normally. Then i decided to look at avast "troubleshooting" settings, and disabled rootkit scan at start up and also quest user settings. After doing those Windows booted up normally with avast enabled. I think it was most likely the rootkit scan option that somehow prevented Windows from booting normally.
Edit. Want to add, that couple of times it went through the welcome screen and then the screen went black (like in 'xma1e' case) and booting hanged. The problem is now solved by editing some avast settings, like mentioned earlier.