Since last night, and all during the night, my rigs have all been stalling out every 20 minutes like clockwork. That is, everything is working fine, hashing away, but suddenly no shares will be accepted after ~20 minutes or so of normal function. Cgwatcher eventually reboots cgminer, even though cgminer didn't freeze and is to all appearances still hashing away. Config hasn't changed on my end and was previously working great.

So I conclude it's gotta be server issues. I end up with a ~12% loss of hashrate because of this.