Marc P.,
Really, all I did was pull most of the cards and reinsert in different slots - under the belief that the Audigy and another card(s) weren't "playing nice"... Shared IRQs and all that...
Yanked everything (sound card, modem, USB/FireWare card, & NIC), except the SATA PCI card and video card (AGP 4x). As the sound card was in the second PCI slot under the AGP video card, and since this was the one I was trying to "fix", I reinserted this first - at the other end of the mobo (bottom PCI slot). Fired up the system and it seemed to work fine (normally, audio was OK, but when going online, audio was filled with loud, high-pitched chirping and other nosies) - no problems online either. Reinstalled the audio drivers - mininmal install - just the needed drivers sans all the other "junk" software (music player, sound editor, etc.).
Started reinserting the rest of the cards, rebooting after installing each one to make sure there wasn't a problem with them.
In the end, best advice would be to pull all unnecessary cards and reinstall the one you're having the problem with, rebooting, and installing minimal drivers/software. If that slot doesn't work, shut down and move up/down a slot until it works properly. If none of the slots work, it's time to move one of the cards that wasn't initially removed (in my case, the SATA PCI card), put it somewhere else, and restart the sequence with the problem card...