After upgrading from 12.04 to 12.10 on my Dell Laptop the wireless was kind of nuts. After boot up, sometimes it worked, sometimes it did not work. Changing from Unity to Gnome3 and viceversa seemed to have some kind of random magic that made the wireless work sometimes.

Anyway, I figured out that I had both WICD network manager and the regular one and they were conflicting for some reason after the install. I got rid of WICD and I have not gotten the problem anymore, every time I boot up, I got the wireless working.

Just in case you have the same problem...