There have been a lot of reports / issues with Creative Sound Cards + Nvidia motherboard chipsets and the issue your describing.
The reason has been pointed at how the sound card communicates on the pci bus and the chipset and they (Creative/Nvidia) tend to point fingers at each other with this issue.
One possibility is with any GuildWars audio engine updates, it caused this situation to happen by how it uses sound, where before it did not trigger it.
Try this. Rename the gw.dat files and let guildwars re-install/download enough to be able to log in and map warp 1-2 places to see if the issue is still there. If it not, then it may be issues / corruption with the gw.dat file, and do a re-install. If same issue, delete the incomplete gw.dat file and restore your fully download one by renaming it back.
This utility will remove any traces of drivers from the system to make sure it's clean -
http://www.drivercleaner.net/ (I use the free version).
Also may consider this: Grab the most current version or the X-Fi driver. At this moment it's newer then the Audigy 2 driver. Use winzip, winrar, etc to extract all the files from the exe. There will be a folder that labeled drivers. Run the installer inside the driver folder to see if creative slipped in newer drivers for older cards where it could takes months for these drivers to show up on there website. I've found newer drivers for my Audigy 2 ZS card this way from time to time.
