samba - May 2013 - samba upload crashes system

Hi,

I've got a modded NAS with a patched kernel 3.8.3

whenever I try to upload a file larger than a few bytes from windows,
the nas crashes completely. Creating folders, downloading and browsing
works fine.
I could not find any entry in the logs.
Everything else works fine, the kernel usually is stable except this
samba issue.

How do I hunt down this problem?

thanks for any help,

JPT

Software details:

I've got SuperCopier 2.2 Beta on windows which handles all file copies
from explorer to avoid those annyoing Explorer bugs when doing SMB
transfers. But this problem also happens if I use other tools to transfer.

Linux NAS 3.8.3.duov2 #89 Sun Mar 17 17:08:16 CET 2013 armv5tel GNU/Linux

debian squeeze

Samba version: 2:3.5.6~dfsg-3squeeze9 armel

/etc/samba$ testparm -s smb.conf
Load smb config files from smb.conf
Processing section "[homes]"
Processing section "[Upload]"
Processing section "[Videos]"
Loaded services file OK.
Server role: ROLE_STANDALONE
[global]
        workgroup = TEAM
        server string = %h
        log file = /var/log/samba/%m.log
        max log size = 50
        load printers = No
        dns proxy = No
        hosts allow = 192.168.20., 127.

[homes]
        comment = Home
        path = /home/%S/Dokumente
        read only = No
        create mask = 0640
        hide unreadable = Yes
        browseable = No

[Upload]
        path = /media/DATEN/incoming
        read only = No

[Videos]
        path = /media/MEDIEN/Video/