As far as I can see One solution only:
Fresh install of windows.

To avoid same problem or to nail the problem;
1. Fresh install of windows XP
2. Update to the latest windows XP
(including media player,direct X graphic drivers if needed etc..)
3. Install CPA 9
See or the problem has gone.
4. Install the other audio and midi software and after each install restart and see or CPA 9 still works.
Once the problems come back at least you know what's the cause.

Allthough a bit time consuming still faster as looking for a problem which can't be traced.