I had problems using the Ubuntu 9.04 rt kernel package, but when I compiled the
188.8.131.52-rt?? kernel from source it worked pretty well, even with the nvidia
drivers. I remember doing lots of other tweaks and recompiling a few programs
also, but cannot remember them now. You could try rtirq? Remove pulse.
Also, FYI I'm using M2496 card also. In the end I removed enough things to make
it not the best for general usage, but pretty good for audio. I have not
switched to 9.10 yet.