I have a Sound Blaster Xi-fi, latest drivers, on vista 64 and I'm experiencing a lot of popping sounds and weird audio anomalies.  Any suggestions as to how to fix this?

Make sure it's not your speakers first, by plugging in some headphones.

Also make sure your cellphone is off or at least 6 feet away from your speakers.  If your speakers have what looks like a black cylinder in the speaker line, before entering the speakers, then they are shielded.  If not, you might want to start there.

you could check your vgclient.ini's sound section... I highlighted some options id check first

[ALAudio.ALAudioSubsystem]
UseEAX=False
Use3DSound=False
UseDefaultDriver=True
CompatibilityMode=False
UsePrecache=True
ReverseStereo=false
Channels=32
MusicVolume=1.000000
AmbientVolume=1.000000
SoundVolume=1.000000
DopplerFactor=1.000000
Rolloff=0.500000
TimeBetweenHWUpdates=15.000000
DisablePitch=False
LowQualitySound=False                                       
IsactStreamPacketLength=250
StreamIsactAudio=True
IsactMusicStreamPacketLength=250
StreamIsactMusic=True
OpenALDeviceName=Generic Software         Try using Generic Hardware or vice versa
MasterVolume=1.000000
Distance=0.500000
Diplomacy=0.700000
UI=0.700000
Creatures=0.500000
Speech=0.700000
Footsteps=0.600000
Spells=0.700000
Combat=0.500000
Environment=0.800000
CombatMusic=0.400000
AmbientMusic=0.400000
UseSpatializedVoice=False
EnhancedDenoiser=False
UseVAD=False
SpatializedVoiceRadius=0.000000
LocalZOffset=0.000000
MaxEAXVersion=0
UseVoIP=False
VolumeScaleRec=0.000000
VoiceVolume=1.000000

Also make sure you have the latest OpenAL installed

connect.creativelabs.com/openal/default.aspx