I have dual boot system with Windows XP Pro and Ubuntu 9.10 on same HDD. There is and irritating issue with Creative Audigy SE where the card will work under one OS, but not on other (so either it work with XP and not Ubuntu, or vice-versa).
Any suggestions?

I think I narrowed down this problem. It looks like it is bad idea to just restart when switching from one OS to other, so far turning off and starting after 5-10 sec worked fine

That is actually a pretty rare issue, although my dell inspiron 1501 had the same issue. It turns out that the laptop wasn't "letting go" of the sound card during reboots, and the new OS was trying to access the device at a different 'location' than the linux partition. I'm not really sure the technical description behind it, but one of the articles I read said to disable the dynamic IRQ assignment in windows, and manually specify the sound card's IRQ in the bios if it's available.