Average after 24 hours: 10.47GH
What hub are you running it from? I only see this on hubs below 2A or cgminer 4.2.3. If you have min 2A hub you should get around 12.5GH even over 24hrs. Just kicked off 24 hrs test to see what I get on my hubs. Also why are you getting HW errors on cores? I get none (maybe 1) without OC.
I have been testing different versions of cgminer and I found that 4.01 works almost flawlessly. On 4.2.3 I get usb errors and random crashes, and slower speed. Any idea why 4.0.1 works so well but not the new version?
Probably not enough power then. Does it only initialise 5 chips if it can't power up all 6?
The usual reason for an older version working better would be: sheer coincidence and nothing to do with cgminer. Though of course any bug is possible, however I'm not seeing the instability you speak of. The only change in the bxf driver between those versions was making bxf bits configurable on 4.2.3. What OS are you running it on? Are you giving it any extra options, bxf or icarus?