Ya know, I'm not sure, but I'm gonna say the reason you're experiencing this now and didn't on the TNT is that the RAMDACs on your new card are much better and are made with much tighter tolerances, and maybe the TNT was bleeding images or had a lazy refresh rate or something.
This is either being caused by a software problem, your card, or your monitor. You can RMA your card and see if a new one does it also. You can also format your HD and see if it still happens. If neither of those are the cause, you need a new monitor. My above explanation reveals how it could still be a monitor problem even though you didn't experience it on the old card.
I suggest you try another (crt) monitor, as that will rule in or rull out the monitor as the cause, without you having to format or RMA your card.
Monitors vary in the type and amount of phosphorous used on the screen, if there's not enough, it won't hold an image long enough and makes flashing more readily apparent. This is why some monitors advertise "flicker free operation" even at 60hz, their phosphorus holds the image for a long time and the images bleed. The downside is known as 'trailing', or 'ghosting'.
Me: are you saying I can't provide?
Me: cause I know I can provide.
Me: oh and I can provide money too
Rachel
: why do we need money when we can just stay in our room and have sex all day?