Unity 2D is crashing at Ubuntu startup

view full story

http://askubuntu.com – I have Ubuntu 12.04 64 bit installed on my laptop along with dual-boot Windows 7 HP. Ubuntu was working perfectly all these days but suddenly Unity 2D is giving some problems. Unity starts with the system correctly but when I hover my mouse on any icon Desktop hangs and Unity restarts after sometime if I try clicking say the firefox icon it opens firefox and the unity 2d completely stops working. I cant see close button on top of the window. and only Ctrl+Alt+Del works, (HowTos)