I seem to have this problem as well, but the flickering is much heavier and makes my external screen unreadable. I upgraded from karmic a month ago. I have an ATI X1200 in a Dell 1521 Laptop, with an external 23" LG lcd monitor (wich is the only display that shows flickering). If I use radeon.modeset=0 the problem dissappears and I get much better performance.
I seem to have this problem as well, but the flickering is much heavier and makes my external screen unreadable. I upgraded from karmic a month ago. I have an ATI X1200 in a Dell 1521 Laptop, with an external 23" LG lcd monitor (wich is the only display that shows flickering). If I use radeon.modeset=0 the problem dissappears and I get much better performance.