To use Service pack 2 and Fireface 800 you need:

1. Make sure your FireFace firmware version is: 2.04
if not:
Go to: www.rme-audio.com 2. Download the updated firmware version
If it does not accept it the first time, try again, RME reports that some users had to try 4-6 times. If it still does not work, try using a different computer that is also online.

3. Also go to the support.microsoft.com and download the XP Service Pack 2 FW (kb/885222)

This will allow FW 800 performance.