Arrow key problems

I've just re-installed Doom 3, because i got ROE today, but when i try to make Move left and Move right use the Arrow keys in the control setup it thinks i'm pushing Shift instead, and refuses to recognise the arrow keys at all..any ideas?

first delete your DoomConfig.cfg and try it again.

Or if it still persists, try this:

While in the game, bring down the console by pressing ctrl + alt + ~ then type this

bind LEFTARROW _moveLeft
bind RIGHTARROW _moveRight