Also try tightening the U1's Allen key bolts a little. On my 3 ants (that's a total of 6 bolts) 2 of them were fine, 2 needed half a turn and the other 2 were very loose needing over 1 full turn.

I haven't done them up to superhero tightness, just nipped them up. May help with heat & speed issues. Just for ref, my 3x ants in a raspberry pi (with powered hub) tend to average 0.40 or lower HW errors (they do have fans cooling them however).

Most Ant's will experience issues if overclocking to 0A81 (2.2ghs) due to voltage and obviously heat issues. My CGminer takes about 15-20 seconds to initialise and start mining.