I notice that you mentioned that you "had to" wipe and re-install from time machine. Could your *original* problem be still biting you? ( "Note: If you're asking for technical help, please be sure to include all your system info, including operating system, model number, and any other specifics related to the problem." --- as stated above the box when you post)

That grey reboot screen is a hard fail. It could be caused by your HD file system being messed up (did you format before you restored?) . Try booting off your system install CD and run disk utility. Check the SMART status of your drive. Figure on replacing the HD if it says anything other than "verified". Run repair, if SMART status is "verified".

If that doesn't get it, you'll need to check other hardware. You can check your keyboard/mouse by substitution, or removal. Remove all other plug-in devices, also. If you find no joy, you will need to run your Hardware Test (if you have it)--- or open the machine to check RAM sticks and other cards.