I had this happen once, last Friday. It attached to a favorite network that wasn't present, and I couldn't get it to disconnect. Switching to offline mode didn't help, it would claim it was connected to my work connection even though I was at a friends' house. I ended up rebooting.

I don't think it's related but the only things that might have affected it: I am booting from MMC, I do have maemo services to disable metalayer crawler. I have no statusbar or desktop apps.