Confirmed with ATI Radeon HD 7750 and AMD Catalyst 13.1 on Ubuntu 12.10 . In many cases (but not frequently) the whole screen turns black for a few seconds (1 or 2 seconds).
The blinking rectangle corresponds to a console cursor at tty7, i was able to see the console's text, but I don't know how to reproducte this effect.
Confirmed with ATI Radeon HD 7750 and AMD Catalyst 13.1 on Ubuntu 12.10 . In many cases (but not frequently) the whole screen turns black for a few seconds (1 or 2 seconds).
The blinking rectangle corresponds to a console cursor at tty7, i was able to see the console's text, but I don't know how to reproducte this effect.