The problem is more than likely your AirPort Extreme equipment-probably the base station. For some reason, Extreme wireless seems to have several issues going on, and it gives a lot of users problems. I had not heard of Samba being a major problem, but I'm not surprised at anything from Extreme any more.
I have yet to move up to 802.11g wireless. Just about everybody that posts about Extreme posts about problems. Extreme (and other vendors' products)haven't shown me any major features other than the promise of higher speeds, so I haven't been motivated to change anything.
Everything I have is 802.11b, and it's working fine. If I need a faster connection than that, I have some Cat5 cable lying around, and I connect that way-it is at least twice as fast as "G" wireless, anyway!