hi saratoga and thanks for your reply.
looking at
http://www.rockbox.org/wiki/MajorChanges was the first thing i did of course, but it isnt very detailed.
that is why i hoped to get some further explanations here, especially on the database problem.
i still hold a backup of 3.13 and the database files are simply not accepted, although (at least) the filenames are equal. rockbox always asks for creating it form scratch.

i also have the emulator running my 3.13 build. is it possible to export the database to txt for instance and import it in clip zip? i would really like to keep all my stats.
p.s.: i never tried going back to a previous build. is it possible to overwrite with 3.13 again without running into troubles?
p.p.s.: btw, i sometimes had 'corruption' issues after refreshing the database leading to recreation as well. (filesystem is ok)