Happened to me on Slush's pool. I'm pretty sure it's a bug in the blade as I've let it fail numerous times with the same results.
I've documented this troubleshooting with WinTame2012 on my blade, especially if I'm running 2 proxies on the same IP address even with different ports specified.
I'm also running two proxies at the same time, but I dont think it has anything to do with the proxy. Cgminer was connected to the same proxy and was able to change to its backup pool, but the asicminer blade didnt.