I have a built in sound, the via HD audio. I saw in other game forums that you could gain more fps to see if you'll gain more fps by disableing built in Sound.
So I Did and it gained fps now im getting 25-33 fps instead of the locked 20 fps below on Ultra high player details.
what i did is disable first the sound in device manager, then run nba 2k9. play then exit the game, enable the sound then play nba 2k9 again now with sounds. I have the Pentium D 3.4 Ghz. Overclocked CPU will also give you fps improvements. You have to do this everytime to avoid the 20fps on your 2K9.
you can try this if your having the 20fps ultra high bug. Or buy a new sound card for PCI just dont use your built in sound. I think built in sounds are also getting resources from the CPU.
my Specs: Intel Pentium D 3.4 Ghz, 2Gig ddr2 800, Radeon HD3870 512mb.