Same problem here after I upgraded my A3 from 1.21 to 1.34 2 weeks ago. The router is about 2 yrs old. ... the problem was only on my N-wireless Netgear WNDA3100 V1 adapters. My G clients were fine. Would lose internet access after about 30-40 minutes. I tried every combination I could think of and then solved my problem this way: http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=4165406&CatId=2668
Obviously not the preferred solution, but better than replacing my adapters.
Just like you, the adapter said that I was connected to the internet, I had local LAN access and I could access the router, but when trying to get to a webpage, no luck. I'd be interested in a solution.