using: XBMC rev. 897
Ethernet config: DHCP
System locks up (freezes) when the UTP cable is plugged in but cannot reach the internet (e.g: because of captive portal in firewall). This happens after a timeout of about 30 secs. In those 30 secs XBMC is usable.
Lockup does nog occur when connection is present or when the UTP is nog plugged in.
Lockup reproduced (tested) on 3 other XBOX boxes (ver 1.6 and 1.6b).