When the RoboConf block is enable (in a region) it causes the theme to fail HTML validation. There is a "&" character in the "Copy & paste" text at the bottom of the "Link URL: " section of the block.
#339525 - submitted patch that fixes the following:
-Switching to the Default config for block presets via the URL causes all blocks to disappear.
-Deleting a block preset while using it causes all blocks to disappear until a different preset was activated.
-Deleting a theme preset while using it caused errors until a different preset was activated. Now the default preset is activated in this case.