If powering the rig off for a few minutes results in the same result, then you may have to browse to the Miner Configuration -> Advanced Settings tab and if the voltage is set to 0000, change it to 0725 if you are running at 250 or less frequency then press Save & Apply.

When you re-check the Miner Status page, it will take a few moments before the chips reset and show o's, they may eventually turn to x's though. The trick is to find a stable voltage setting at the frequency you are running at that results in less HW errors, so you may have to increment the voltage. It is an involved process but will surely yield results if you have the patience.