take the keyboard apart and check for buttons that are stuck on with a continuity tester. the more used buttons get stuck sometimes, unsolder the stuck button and use one of the buttons you don't use, like the online button to replace it. If you still have the old monitor there's a few buttons behind the F keys.

If the keyboard itself checks out then the controller for it might be the problem. Check it for loose solder joints. if you don't find anything and the keyboard buttons all check out then it's most likely a bad keyboard controller, keyboard to sercom cable or sercom board

if you are in north america txt me 706-627-7854 I might be able to find you used parts if you need them. I build conversions for these lasers that run Win XP.

Chris Krug http://krugtech.com/
Maximum Up-time, Minimum BS

Now the problem is fixed. I didnt do anything. At last friday just cleaning cabinet with compressed air and turned machine off. Monday morning i tried to turn it again and it works. I dont know what happened. Maybe something overheated?
But thanks for help Krugtech!

sometimes just pulling the boards out and blowing out the connectors in the cnc rack is all it needs

Chris Krug http://krugtech.com/
Maximum Up-time, Minimum BS