This upload limit is an old issue now, and unfortunately, it is still not solved :
the prblem comes from the way lighttpd/fastcgi scripts are handling upload…
i finally found that the limit of file that will succeed to upload will depend on the amount of cpu, memory ressources / bandwidth available…
==> i had limited the size to 8MB thinking it would enough in main mybooks…. but if you have installed other hacks, or use the memory of the mybook, it could explain why you have this behaviour….
unfoirtunately, this issue is now an old one, and i never found a solution for this….
What you could do is to use FTP to upload your files : you could install the vsftp feature pack which allows to upload via ftp to your Mybook….
On the Whitelight, because i use php, this problem has been solved and the upload limit has been set to several hundred of MB …..