That happened to me too, after the firmware upgrade it automatically changed me from stock 218.75 to 237.5 and the hashrate went down to 100 Gh/s with the frequency not showing up in the console. If you change it to 218.75M or 250M in Advanced Configuration, however, it goes back to mining at rates you'd expect at those frequencies. For whatever reason the upgrade switches it to 237.5 and it simply doesn't work.

Interestingly enough, if I SSH into the box, the asic-freq file shows me running at a different rate than the Advanced Settings tab and the status page show. Whatever they did in the firmware upgrade apparently bypasses the asic-freq file to make the changes. In any case, I have my four 'well-behaved' miners running at 250W now, and the two trouble children that don't OC well running at 218.75 on the new firmware and all seems fine for now. But agreed, the firmware update didn't seem to help much and makes me a bit nervous now.