Shutdown problem-MCI Command handling window error

Hi friends

After using 5-6 hours if i try to open internet explorer it get hanged. other application works fine but ie doesnt. when i try to shutdown no logoff,shutdown, no restart possible and after some time its shows mci command handling window and after that it show only a blank desktop with no icon. If i get the pc manually restarted then everything work.

Workgroup Computer
Operating System: Window 2003 sp 2
I.E : I.E 7.0

Hoping for ur suggestion and reply
Thanks