Ok from what I read it seems at very low temperatures some cpu's won't boot, calling cold bug sounds a bit dubious.
I would think this a suck it and see kind of situation, not all cpu's encounter this problem at a certain temperature.
However most people who do encounter this "bug" are using liquid nitrogen cooling at around -20C.
I would think a Vapochill system probably won't reach these temps without a bit of help, but adjusting your lowest temperature will probably allow you to avoid the bug if you encounter it.
And really do try the other extreme overclocking forums, cause they are the only kind of forums you are going to get help on this kind of stuff. Becasue those temperatures are completley undocumented, untested and unsupported by AMD and will only every be encountered by the people in those extreme OC'ing fourm as you can see from the overwhelming response you got in this forum
But do report back on far you do manage to overclock your opty