Network manager doesn't work well for me either between home and work.
I usually use Ethernet at work and wireless at home. That's fine.
But then, if I need to use wireless at work, my wireless settings get screwed at home. "Auto" settings don't help. Somehow(*) the network manager remembers gateway or DNS settings from work and apply them at home. I have to set them to a fixed value as a workaround.
(*) I have not enough knowledge of network settings to tell exactly what happens. I would need help.
I don't mean to hijack this thread... I just want to point out that there's possibly a bug in default gateway and/or DNS settings in network manager.