Not aware of sudden sound probs on xp en masse per se, however, Creative who are by far the biggest supplier of sound cards globally, messed their customers around terribly with Vista. Essentially, they failed to support a large part of the range as a means of forcing people to but new cards with Vista support. A clever user hacked their drivers to make them work, they barred the guy, Daniel K, from their forum & thretened to sue him.
The subsequent outcry and ensuing negative publicity forced them to relent & co-opt the guy into their community. Even now, the only working driver for Xfi extreme gamer on windows 7 is a Daniel K one. Creative are not well regarded over Vista.