You're not the only ones having problems with Linksys gear and BT:
http://www.dslreports.com/forum/rema...lehw~mode=flat
That's the best info I can find right now...I've been reading about similar problems for a while now and I remember seeing this a ton of times, apparently it's a Linksys chipset thing that balks when BT opens tons and tons of high-bandwidth TCP connections like it always does.
I think the firmware update may fix it though. If it were me, I would troubleshoot the Mac connection problem rather than try to troubleshoot an issue that may be fixed in firmware.
Finally, did you set your router up for port-forwarding? If nothing else works for you, I have a gut feeling that forwarding ports 6881-6889 *might* fix or reduce this problem, plus your upload/download speeds would go faster...