I know this sounds little wonky - but have you tried removing any card in PCI slot 1? It shares an IRQ with the AGP slot, and it might be part of hte problem. Likewise, a soundblaster card and a network adapter shouldn't be in paired slots, either.
Being in 2x mode isn't fabulous, but it's good enough to get Wine to work so that I can play EverQuest. I can't really complain. It's far better than I've had it working before.