I has been running Ubuntu 32 bit from versio 5.04 to 12.10 for serval years now and used Virtual box (not on the erly 5.04 and so) but when it became avalible. Never got any problems at all.
Now I am running Ubuntu 12.04 and 12.10 64 Bit. I can't get the Network Bridging to work, it wont give me an IP from my network. It works fine if I use NAT. But that's not what I need.
If I install 12.10 32 bit on same computer it works fine.
I got a Dell E6430 i7 3630QM with 8Gbyte RAM.

Best regards.
Rikard Svenningsen