I've noticed this myself.
Normally i run with headphones on, occasionally using speakers. Where i get trouble is when switching from game mode to music mode.
If i switch modes and change to 5.1's and forget to switch back to headphones before i shut down the pc, i find my sound card with compatibilty issues. (so when i turn the pc back on, it is in gaming mode, shows headphones, however in a deeper layer of the sound cards programining, it still has 5.1 mode from the entertainment interface).
Now this leads to why i posted this. If i take the time to make sure both modes match the speaker type, i don't get the odd popping noises underwater and in certain overland areas.
Might be rare, might not be connected, but ya never know. Oh, and there are new creative drivers out now. If you download them, it changes your interface, thus changing all of your settings. Don't forget to redo them.