I have seen something similar to what you describe on aggressively compressed LAME encoded VBR files. The only way I got round it was to whack the files, re-encode after dropping the quality, and try again. What I then found was, the disk access icon was coming on very frequently, and stepping track forward/trackback became laborious. Only withLAME encoded files (this is on a Mk 1 with only limited RAM, don't forget).

I've actually stopped using VBR LAME and gone back to the Xing AC encoder - I have more consistent results with better VBR encoding. I suspect when VBR in LAME evolves a little, it will be less agressive and I will go back to trying it again.

One of the few remaining Mk1 owners... #00015