I experienced this identical bug after upgrading from Hardy to Intrepid. Network Manager didn't segfault, but it would refuse to connect to any wireless networks. I finally fixed it by running 'apt-get remove --purge network-manager' followed by 'apt-get install network-manager-gnome'. This last step installed an additional library that hadn't been present on my system, but since I was in a hurry to get my machine working after the upgrade, I forgot to note which library that was. I hope this helps anyway.
I experienced this identical bug after upgrading from Hardy to Intrepid. Network Manager didn't segfault, but it would refuse to connect to any wireless networks. I finally fixed it by running 'apt-get remove --purge network-manager' followed by 'apt-get install network- manager- gnome'. This last step installed an additional library that hadn't been present on my system, but since I was in a hurry to get my machine working after the upgrade, I forgot to note which library that was. I hope this helps anyway.