I installed the full GB RUU and the wifi problem persists. The phone states it is turning on wifi, momentarily shows that wifi is on, before greying out and stating turning on, repeatedly.
Just in case you missed it, see my post above. "Search.. Connect.. Disconnect.. Search..." is the exact symptom that newer cards (with newer drivers) seem to be having when things like SpeedBoost/AfterBurner are turned on in a Linksys router. I suspect many other manufacturers had their own proprietary speedup technologies back in the days before 802.11n, and those may be problematic as well.
Thinking on it, I believe all the cards I had this problem with were (like the Thunderbolt's), 802.11n capable cards. I do know that it always happened after a driver update - the device would work just fine for a long time, then a new driver would cause it to go into a connection loop and no WiFi.
I suspect, though this is just a guess, that SpeedBoost/AfterBurner is a pre-draft-N technology, which means it's using something similar to 802.11n protocols to enhance speed, and probably something inspired by 802.11n, but not quite similar enough to actually work. Just similar enough to confuse the wireless card into thinking it can fire up an "N" protocol, but not enough to actually make good on that promise. So the card tries "N", receives no reply, and starts over.
Check your router carefully for any possible "speed booster" technologies, and turn them off.
As a workaround/test, you can turn off wireless encryption (set the router to "open" rather than WEP or WPA/WPA2), but that's a poor workaround if you want a secure connection. Plus, it only worked for me on the one device I actually tested, so I can't call it a workaround for all devices anyway.