thanks for your replays.
@Ricky_Tech1984: w8ing 5-10 min sometimes solve the problem some time i just press the shutdown button and go to work, after i come back the computer was turned off.
i solved the problem. (sorry for not posting this earlier)
the problem was that i enabled the "auto hide the taskbar"
when disable this option all work OK
i dont know y its happening, i always configure it this way and i never had any problems, i work with win 7 on several computers and specifically my home computer is giving me this hard time, all othe computers i work on (with win 7) working great with this option enabled.
any 1 know how to solv this?
if not... so forget it, its not that a big of a problem.