Ok, after messing around a bit, I can duplicate this. Maybe this is not your exact issue, but I can consistently screw up the arrow keys.
Renoise 2.1 (and others), OSX 10.6.2: Steps to reproduce:
- OSX System Preferences -> Enable “Spaces”
- File -> New Song
- Press the down arrow 10 times.
- With your left hand on the left CTRL key, press the up arrow (CTRL + UP) - substitute CTRL with your “Switch Between Spaces” shotcut(s), see screenshot below
- Now, try navigating up or down in Renoise. (The arrow keys are fuxed now)
If you disables “Spaces” (and restart Renoise, or CTRL-Arrow again) the problem goes away. Probably because the shortcuts conflict.