You can get the frame rate right by dragging a clip in question onto the Make Comp icon at the bottom of the project window.
If you're fooling around with time -- time stretch, time remapping, posterize time, time displacement -- or using Rotobrush or Warp Stabilizer -- you should know that AE doesn't like mp4's as the source video. No telling about the avi.
There could also be compressed audio in the video files, and AE has never played nice with compressed audio.
Standard answer: Extract/ separate the audio in another program and convert it to a WAV. As Dave said, even after all these years, AE sucks at certain types of audio.
No, not even a single stretch.
Compressed audio? Any way to tell?
Here's the short version: if it's NOT a wav or aiff file, it's compressed.
The solution seemed to be double-klicking the Ram preview button when playing. Fixed both the framerate and the sound. Sorry for taking your time. The only thing is it now restarts when it hits a blue or grey are on the rendering timeline. I wouldn't be suprised if this is normal, but still....
Edit: Turns out I never understood how it was supposed to work. I'm getting the hang of it now, thanks anyway. Sorry for bothering you.