I've just bought a Asus Xonar U1 external USB sound card for my laptop (HP Pavilion 9045) and I'm having trouble with choppy sound. It seems no matter what setting or what output (I've tried with the SPDIF with an optical cable to my reciever, and with a pair of earbuds), I get choppy sound. The worst is with mp3's in iTunes but movies (with or without 5.1) is choppy in vista media center and the problem is solved by removing the sound card. Yesterday I connected the device, uninstalled it and reinstalled it. This solved the problem for some time and I was able to watch a movie in 2ch over PCM, I tried several movies in 5.1 (with Dolby digital live enabled in the settings) which worked fine. Even iTunes worked with 2ch over PCM a little while and then without me doing anything it started to get choppy again. Any suggestions?