When I flash 29beta1, my ac66u goes into recovery mode with the power light blinking.. I was upgrading from 28beta 1. I had to revert to 28beta1 with the firmware recovery utility to get the router to work again. I tried upgrading about 3 times and the router always goes to recovery mode. Should I try resetting the router to factory defaults and trying again? or just wait for the next version? very strange
Occasionally I came up with the same problem. After a firmware upgrade from WebUI, the router restarted itself, then the PWR led kept blinking just like in recovery mode. But it was not recovery mode because the ASUS recovery utility couldn't communicate with the router.
If unplug the power cord, wait for some 10 seconds, and replug-in, there's a high probability that the PWR led be off, only the LAN leds are lit. The router would be brick at the time, even pressing reset before power up doesn't work.
My solution, so far always works, is to unplug the power, wait for some 10 minutes, then press the reset button and plug the power back in. Then use ASUS recovery utility to upload firmware, which could be either old or new in version. And it's better to give the PC a static IP like 192.168.1.2 before using recovery utility.
I guess it may be safer to restore to factory default BEFORE and AFTER a firmware upgrading, like people do with dd-wrt. This method solved my weird WAN DNS manually setting not working problem.