Can anybody please advise me.

I have been successfully burning dvds on Adobe PP2 for some time using the presets. Suddenly I have lost sound and am burning silent movies !! I hadn't changed the preset in any way. However, in an attempt to get sound back, when I changed the audio option on the preset from PCM to MPEG I could successfully burn the dvd with sound. I understand the quality of the sound will be diminished using MPEG. Do you think this is a software glitch or maybe something to do with my burners? Any help would be greatly appreciated as I'm pulling my hair out !
Thank you.