its a mk2a, the highest fid i had on it when it stopped to work was 701f (that is, 701f0 and 701f1).
in the serial-output it would always say:
! playerdb.cpp : 182:Failed to build dynamic database (status=0xc004401a).

i think i really tried everything - reinstalling different player-software-versions (v1.03, v2.0 betas) and those fsck-procedures, but nothing did help.
there was no other way than deleting the last fids i added, after doing that it worked again.