VirtualBox 3.0.12 on Fedora 12 gave me the same error message when registering. The first time it looked like the two IP addresses listed in the dialog were both ones that I had at different times with my AT&T DSL (one being my current IP, the other being an older one).
I tried later and clicked to register 3 times. It gave me an error 2 times, but the IP2 listed was completely different in both dialogs. The first dialog said this:
Failed to register the VirtualBox
Invalid IP address.
(the first was my current IP)
The second time the IP2 was a 216.x.x.x address. The third time it finally said the registration was successful.