I'm getting a weird shadow/smudge problem with my Viewsonic

Viewsonic VX2025 LCD. At first I got these visible waves (lines) down the screen and I would get shadowing/smudging after letters/icons/e.t.c. We found out that the former problem was due to electrical interference and we fixed that but we don't know how to get rid of the shadow/smudging problem. It's like you can see double after an icon and after words you can see the last two/three letters of that word shifted a bit to the right of the original position of the word. It's an on and off problem, I don't know what causes it. Usually I switch off the power from the monitor for a few minutes to get rid of it thus I thought it was due to the monitor overheating as everytime it happened the monitor was pretty hot, but that's not the case now as it's ice cool and I just got the problem again. I've updated the drivers so it's not that. I would appreciate any help with this problem.

It has d-sub too, and he didn't mention what kind of connector he utilized. It sounds very much like analog signal interference to me, so if he's using d-sub, I would suggest buying a DVI-D cable and using that, unless the video card doesn't support it, then just get another cable and see if it fixes the prob.