Just a small update: it turned out that the sending through Amazon is actually the main reason of this issue - 0x103 behaves just fine when sent over usb too. And the reason is quite clear when looking at the filenames returned by Amazon - they are all different, containing some asin sequences and more... So this whole thread and my testing was rather pointless, I should have noticed the real problem immediately.
EDIT: However, of course it does not diminish your help, Kovid - thanks a lot for that! If nothing else then at least I learnt something again.
Last edited by janvanmaar; 11-16-2010 at 08:56 PM.