Reporting in with an odd problem.
One of my S5's went to hashing at half it's capable rate, despite all rows showing o's. A reboot resolved the issue.
Running stock firmware from B1.
People have reported that the newer firmware solves that issue.
I'm scared of upgrading

Guess I'll take the plunge. Thanks !
Edit: Updated CGMiner in latest firmware. Cool ! So far so good.
Hi.
The new firmware (Jan 7) does not include a new CGminer, it's still 4.8.0. If you also want to install 4.9.0, then that's a manual SSH operation which does not survive reboot. Here are the instructions: