I don't know if this is normal or not, but I've finally decided to address this issue. The audio for some of the sound effects will be silent sometimes, like when I'm casting a spell. I won't be able to hear me casting a spell, but the sound effects for it does come back eventually though. Also, in some cases when someone is speaking, if I go to the inventory menu or something and come back, the audio for the dialog will be silent until it finishes the paragraph.

Yeah, fairly standard. I lose spell sound affects regularly, if I cast the same spell several times. If you switch to a different spell, (don't recall if you actually have to CAST it...) then go back to the one you wanted, sound affects come back.

Ah, so is there no permanent solution then?

Not that I have ever found...... I just don't worry about it. Oblivion has its quirks......