Trouble with wifi

I have a 2009 macbook (polymer case). The airport started cutting out a few weeks ago on me. It turns off and I cannot turn it back on. Initially rebooting would resolve the problem, at least for a half hour or so, but it no longer does. I've tried all the tips on this site:
http://osxdaily.com/2009/12/22/mac-...ooting-airport-wireless-problems-on-your-mac/

to no avail. I've also tried changing the port service order so that the airport is first, also to no avail. Any more suggestions?

 

I'm running 10.5. The trouble seems to have started around the same time as my last software update, but I'm not positive the two are related.