SP2 borking sound?

I’m running SP2 on XP Pro, and having trouble with my Audigy 2. There is a slight pop when a sound plays, but not on every sound. For instance, when I run the speaker test in the Audigy 2 control panel, the test that names the channels doesn’t exhibit this, whereas the test that plays white noise does. I can also hear it if I play an MP3 file, and hop around the file using the media player slide. It’s subtle, but annoying, and makes some games sound quite bad. It used to be really bad in certain games like Motocross Madness 2, when there was a lot going on, the sound would break up badly. A fix I saw was to reinstall XP with the non-APIC ACPI HAL, which definitely improved things, but not fully. I’ve tried everything – fiddled with latencies using powerstrip, muting mixer settings, etc. I posted a while back on hardforums, and somebody responded that their sound started breaking up after installing SP2, so I reformatted and tried a game without installing SP2, and sure enough, it was better. Has anybody had any similar experience with SP2? As I said, the effect is quite subtle, and might easily be overlooked, so check it out – the best test I’ve found is an MP3 of dialogue (I have a lot of comedy files) and hop around the file as it plays. I’ve reproduced this on my old P4 machine using both the onboard sound and my Audigy 2. My current machine is an A64 3200+ on a KV8Pro, with all drivers up to date.