any other ideas?
i will not be able to help you very much... but when i was with planetccrma (redhat 9, kernel 2.4) i had the same problem. running 2 pd doesn't help at all. i've switched to gentoo, with ck-kernel 2.6.11, i'm using jack (of course), all in -R, -rt and now no more glitch when doing gem / pdp and sound. i'm using a nvidia by the way. i didn't try with an ati.
patrick