W500 and Jittery External Monitor on mini DV port

[FrankK-F]

When I reboot the external monitor [DELL 1600x2560] displays stable.

When I awaken the W500 the external display jitters .. horizontal about 10 pixels. If I go to 'Screen Resolution'
and change a screen setting [native or external], the external's jitter stops; I press 'Revert', then reset monitor to default [max] resolution. This suggest that I have a SW / Registry problem??

My video driver version is ATI Mobility FireGL V5700 version 8.792.5.2000 5-4-2012; W7-64 / 8GB memory.

This misbehavior started several months ago, is consistent, and has become a real nuisance.

Anybody with same issue? Any fixes?