dual-screen intermittent blinking/flashing

[SFR75]

I connected a second LCD screen (DVI) using minidock.
Every 2 minutes or so the screen sort-of blinks/flashes.
Exteremely annoying and makes it very difficult to work.
It's as if something is resetting or refreshing it... or changing
some settings. It happends actually every 100 seconds...
Does any1 else has the same problem ? Any clues on how
to fix it ? (I already uninstalled presentation director)

T60p machine
MiniDock
ViewSonic 2030b screen

Help!