I agree with Jim that a support contact would be in order. I have not seen what you have encountered on 2 PCs now and have been running OneCare on many computers for quite some time. Is there perhaps some other security software that you are running concurrently with OneCare?
It would seem counterproductive to be disabling the OneCare firewall and seeing the red status in order to get around this problem, even with the Windows firewall active in its place.
The problem you described used to be common with Dynamic disk partitions, but OneCare will now refuse to install if you have Dynamic partitions.
-steve