I cant remember if it had to do resampling, i hope it didn´t since the cm108 is the newest of cmedias low-cost series. But since resampling should´nt create much problems, especial on the 500gx i cant think of as this is the problem. Do you habe some linux-pc to try it out there ?
As i cant find any bug reports about the given error that give usable information, and dont have the device i just guess the problem.
Do you have the soundcard with the hd on separate ports ? If not this could be the problem forcing the hd down to 1.1 speed...
My Stuff: WL-500g, Mapower H31x 10GB HD, Philips Webcam Vesta PRO, TerraTec Webcam PRO, USB Hub