BeagleBoard XM - Rev C reset problem

Hello all,
i 've some trouble with my BeagleBoard XM - Rev C
When i m trying to upload a file > 500 MB the target always reset.

I ve checked all things like RAM directory size (maybe it could be it
will buffer it into RAM, but RAM is 512 MB so it should not be the
problem).

FTP server is also running.

I 've tried it with different FTP methods like wget, put, python ftp
functions, but it is always the same behavior.
This problem merely occurs by a few boards (4 of 7) but all have the
same images and static ip addresses.

What could it be? It makes me crazy... Maybe the boards are broken??

Regards
Sebastian