I've got a bit of a mystery on my hands with my Sony 21" CPD-G520P monitor.
Not sure of the chassis number, but inside the case there's a sticker with a
few numbers:

SCC-L45B-A
SV-3614(U)
J505279
6000101

The issue is a shimmering rainbow effect on vertical black lines. I first
noticed it around black text on white backgrounds, where there would be
sections of text with red, green, or bluish shadows around them. I've since
found a test pattern program (ntest.exe) that will put solid vertical lines
on the screen (alternating light and dark), which shows the pattern quite
vividly. It's apparent in any resolution and refresh rate.

I have two pictures at this URL:

http://www3.ns.sympatico.ca/pmason/sony

I took the monitor to a local Sony-authorized shop. Before I left it with
them, I had them run the same test pattern using the same program, and the
image over there was perfectly clean looking!
We tried to increase the refresh rates/resolution, but he was having trouble
getting his computer to cooperate so I left it with him to try and figure
out.
Today he called to say he'd run it up to 1600x1200 at 85 hz, and not seen
any signs of what I described. He suggested I try powering the monitor with
a UPS, so I picked up a UPS from work, and brought the monitor home.

I connected my laptop (running on battery) to the monitor, which was plugged
into the UPS (which was running totally on battery, unplugged from the
wall), and the interference was there. I moved it around the house,
upstairs and down, and got no change. I even hauled it out to the car, with
the UPS, and drove around the block with it running, all with no change! I
did notice however that my signal light had an effect on the pattern,
causing it to shift slightly every time the lights came on. Also, when I
rotate the screen left or right, every x number degrees of rotation will
cause the pattern to jump in one direction or another.

Does this sound like some nasty EM field in my neighborhood? I can't think
of anything else that would cause this. My only other idea was to take the
monitor into work when I'm off vacation next week, and try it there. We are
not too far from the repair shop in the same industrial park Other than
that I am out of ideas!

Anybody have any other thoughts as to what the problem might be?

FWIW. I have another monitor, a 19" Viewsonic, that always has had a slight
shake at the edges of the screen. Similar in frequency to the shimmering of
the interference on the Sony. I ran the test pattern on this monitor, and
there is a similar effect, but not nearly as intense... and mosly limited
to edge of the screen. Until now I never gave it much though, it was a
refurbished monitor, but now it seems like it could be related.

Maybe the Sony is just particularly sensitive to EM fields?