Network not working in NAT mode: VirtualBox >= 2.2.2

Situation:
Host: XP 32bits, LAN with DHCP. Two Virtual Machines in VBox 2.1.4, ROS and Win2K. Both with network working correctly (NAT mode: PCnet-Fast III (Am79C973))

After upgrading to VBox 2.2.2 or 2.2.4 network stops working in ROS while it still works in Win2k VM.

Tested with rev 41291, ipconfig says "Media Disconnected".
If I change network settings in my ROS vm to bridge it works.