Videos not playing correctly

[cuser]

Lately when I have played vids via VLC and went forward or backward during replay vids have started to stutter (like replay going back and forth for a few secs) and that continues as long as replay goes on, weirdly only some vids (flvs and mp4s dl'd from youtube) are affected but not other vids (avis, wmvs, etc).

VLC: latest 64-bit (tried with hw-acceleration on and off)

OS: W7 64bit

edit: only 64 bit version of VLC bugs (today when trying to add subtitles it crashed (even 2.1.3 crashed)) so going to stick with 32bit until there's a fix.