Hmm, that wireless adapter might be a problem. I suspect it is sharing with the AGP. That's a VIA based motherboard so we might be on the right track. Could you pull it to do some testing? Does your Soyo manual have an Interrupt table? My ASUS does (with an error or two in it, of course!)

You might consider swapping the sound card to slot 3 if pulling the wireless adapter doesn't help. On my ASUS, slot 3 shares a physical interrupt with the onboard audio. So with onboard audio disabled, it would be a natural place to put your soundcard (assuming your board has the same interrupt table.) The sound will most likely need to be on slot 3 or 4, although it might work best on 5. Also, with my ASUS, the onboard USB controller shares with slot 5.

If your board has the same interrupt pattern (being in the VIA family) I would try:
Slot 1 -- empty (AGP card is there so nothing would fit anyway)
Slot 2 -- empty
Slot 3 -- Soundcard (onboard sound must be disabled.)
Slot 4 -- Wireless Adapter
Slot 5 -- USB hub

I forgot to mention in the previous post, you might want to check your BIOS to make sure any onboard sound is disabled. You've probably already done that...