When I leave my computer alone for a while and the screen dims, it takes a while for it to come back after moving my mouse or typing. It does the same thing if the screen is black. I had to shut down my computer by holding down the power button the other day because it wasn't loading after I had restarted.

Thanks for your help,

edit: It's starting to hang a little bit when I leave it alone for a while. The mouse won't move for a while and then later the screen will un-dim. I also got logged out after it froze.