PPRuNe Pop
I have a similar problem at home, and also in our tower at work. We both use analogue LCD monitors. Both problems are identified as electronic reflections within overly long video cables.
At home I bought a cheapie cable first up and had vertical ripples across the screen, rather like ripples in the shallows at the beach. It was unusable.
I upgraded at considerable expense to a decent quality cable and it's much better, though not perfect. There's a single ripple, not very pronounced, in fact almost invisible on light coloured screens.
My video card does not have digital output and my monitor does not have digital input, so I haven't investigated digital video as a fix for perfection yet.
Similar story at work. There are 6 identical workstations, except that due to space constraints in the hardware cabinet one of them has a considerably longer video cable than the rest. It's the poor cousin, with right hand edges on everything on the display slightly blurred. Perfectly useable, but not as good as the other 5 displays. Being part of a national ATC system, quality controlled (ie, you get what we give you), no mods allowed, etc, etc, all the techs could do was get the best cable they could but it wasn't quite good enough.
Could it be your cable or connectors, both on the cable and at the video card and monitor? They can go crappy, especially if strained - dry joints etc.
Good luck
AA