Seems that the bug that wouldn't allow networking under Virtual Box in Haiku wasn't related to Haiku, as Virtual Box version 2.0.2 allows networking under Haiku (1.6.0 didn't).

Previously the network card would be detected, but resolved the incorrect IP under DHCP, and also wouldn't work with a static IP address. I simply had to use the 'Intel Pro' adapter in the networking preferences and select 'attached to > host interface'. Tested with the latest Senryu .