Where are the 301s taking Googlebot on those IP addresses? And are they the same IP addresses every time? Have you narrowed those IP addresses down to any particular datacenter/country? It could be possible there is some configuration with your server that treats IP addresses differently depending on the country... it could also be that the IP addresses getting the 301s are known blacklisted spam IP addresses but are masking themselves as Googlebot so your server's blacklist software is keeping them out. It's really hard to say without looking into the data myself but I'm definitely interested in what you find out.
