I've been using an API called Record Management System (rms) for saving tracks, because it's designed for this kind of things and I didn't have to handle any paths (which might be different from phone to phone). Unfortunately the rms seems to be limited to 64kb of data per RecordStore on the BlackBerry (and is probably equally limited or even smaller on other phones).

Now 64kb is big enough for a few medium sized tracks or one large one, but then it's full.

I will now change the system to store it's tracks directly into the filesystem (into the directory selected as export directory).

I'm planning on releasing 0.3.1 today, which will include the fix.