I'd recommend smc's firmware 1.4i.4. www.smc.com the model is 2655 if I'm not mistaken. it's been a while. I don't know if it will fix your issue, but I've had really good luck with it. also: beef up your signal strength. directional antenna on the client or even a $230 - 500Mw amp from www.YDI.com. the amp is a sure fix, but I understand it is a bit pricey. if you already have a directional antenna on either end, turn it 90 degrees and see what happens (reverse the polarity). that can cut interference from other APs, phones, etc. I've had gains from this even if it puts one ant horizontal and the other vertical for polarity.
I had the same problem except mine wouldn't come out of the sleep on their own and it turned out they were associating with another AP with the same ESSID and a better signal (unfortunately the other AP was directly connected to the client AP via a crossover cable). That was my head scratcher back in the spring. I must have lost a weeks sleep, but no customers. No fun. Good luck. -- general wireless list, a bawug thing <http://www.bawug.org/> [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless
