C640 and External LCD Problem

hi,

i am having a problem with my Samsung Syncmaster 910T LCD connected to my Latitude C640 through a CPORT II.  When both monitors are on (laptop and LCD), the samsung lcd flickers quite often.  not as in the whole screen goes completely off, but u can see the color not holding constant.  this especially happens when i put the pointer over links on a webpage, or when the cpu is working, like when opening a program, you can see whatever image thats being displayed on the LCD flicker very quickly. 

 

is this a known issue with the c640 and external lcd's?  when i had a crt monitor hooked up, i did not have a problem.  i tried the samsung monitor on a different computer, and the picture is perfect, so i do not think it is the monitor.  i also have the newest version of the M7 driver, and am currently trying the settings on the omegadrivers.net website to see if it will help.  as of yet, no luck.

 

any help is appreciated.