So I went for it and got the Vegas 9 upgrade..
I registered, activated the 64 bit version, but when I try to register, active the 32 bit it wont progress.

There should be absolutely no problems activating both the 32bit and 64bit versions using the SAME key on the SAME machine. If it's not working, there's something else going on.

Have you tried a different activation method? You might want to try "activation from another computer" if you've been trying the automatic method. You don't actually have to use another computer - you just use your internet browser to send your key and get a counter key that must be entered into Vegas.