No Headphones or Cue output [SORTED]

I have no headphone (or cue) output.
Firstly it is not the headphones not plugged in or a volume / cue-mix problem.
On the Audio tab of the preferences I have the choice of Left/Right or None in Outputs 1, 2 and 3. and when changing any of these the other two Outputs go to None. It is also set to Dual Stereo, even though changing that makes no difference to the available choices.
I've re-installed (2.1) and the drivers and it's made no difference. I am now using a PC running XP Pro (latest updates installed). It all works fine on my MacBook Pro running 2.1, but using the MBP is no longer an option for gigs.
Anyone got any ideas as I no longer carry the dual CD players on my rig and am planning on only using Cross / U-Mix from now on.
Firstly it is not the headphones not plugged in or a volume / cue-mix problem.
On the Audio tab of the preferences I have the choice of Left/Right or None in Outputs 1, 2 and 3. and when changing any of these the other two Outputs go to None. It is also set to Dual Stereo, even though changing that makes no difference to the available choices.
I've re-installed (2.1) and the drivers and it's made no difference. I am now using a PC running XP Pro (latest updates installed). It all works fine on my MacBook Pro running 2.1, but using the MBP is no longer an option for gigs.
Anyone got any ideas as I no longer carry the dual CD players on my rig and am planning on only using Cross / U-Mix from now on.