Are you playing on an A1200 or a different Amiga? I could be wrong, but I remember that being a problem across the board and talking to others about it to make sure I didn't have a faulty system.
Anywho, GREAT GAMES! totaly under rated by too many people and should be put back into print:quickdraw:
AND! doomisawesome...
I had also this problem when upgrading my A1200 to an Infinity tower from Micronik - they had the glory idea to be able to use the original keyboard via an keyboard adapter. This was an real step backwards in gaming when using the keyboard so I bought the Keyrah adapter from Jens Schönfeld which worked perfectly then but I used then an IBM keyboard
