Hi Marc,
Yes i have done this test a few times now. It's actualy hard to get my soundcard working again. I succeeded onces but now i am wondering again how i did that before.
Installing, Uninstalling, Reinstalling, etc, both with the soundcard turned on or off, but without succes this time. Tried to reset to factory default a few times.
Uninstalled all virus software again as well. At that point (yesterday) i was about to call in help from T.C. support and switched my soundcard on it actualy worked.
Then i installed OS4 to see if this time it would keep working but after reboot the soundcard failed again.
My studiocomputer:
OS: Windows 7 64bit
motherboard = Asus Rampage Extreme
CPU = Core 2 Duo - Quad core 3ghz
Mem = 8gig 1600Mhz OCZ
GPU = Asus ATI EAH 4890
C: = 128gb SSD (solid state disk) Crosair 220/200
D: = 320gb HDD for instrument libraries
E: = 320gb HDD for backup, other files, etc
Hardware connected to computer that could be relevant to this issue:
T.C. Eletronic Konnekt 8 external soundcard through firewire (latest 64bit driver/software)
T.C. Eletronic Powercore 6000 through firewire (latest 64bit beta driver/software)
Access Virus TI Polar through USB (lastest 64bit driver/software)
In fact i not connect any of the hardware on the computer at this moment i just want sound for listening to music or doing a game or programming actionscript or whatever.
Just as soon as i installed OS4 my sound is gone without even the hardware synth or DSP connected.
What else information you need more, just ask and i will try to give that. 
thanks for the fast reply