Screen problems since last s/w update -- suggestions please

Question

Folks:
I think the most software update I got and installed was iTunes and QuickTime. I think --I'm not 100% sure-- that after the obligatory restart after that update was when I started seeing problems: Font "distortion" in some applications, not consistent, but now characters run together sometimes and characters look, well, lo-rez -- not consistently at all, though.
Here's a somewhat more clear symptom. Adobe Illustrator (CS3, the latest) displays a rectangle around the central drawing area, a 1 pt black line. Operating in AI the rectangle looks fine until I move the cursor toward it. In some cases --right now on the right side only-- as the cursor approaches the line the a segment of the rectangle displaces away from the cursor about one or two pixels. It doesn't matter which drawing tool I have selected.
Here's another symptom: As I type this (in fully updated FireFox) the first non-blank line above is distorted, as if there is a kind of smudge over the lower half of all the characters. This horizontal smudge seems to follow my progress as I type, two lines above the current cursor. As I continue to type, the distortion moves down, and affects only one line. Characters outside this "smudge zone" are fine.
Another symptom: As I move the cursor around over this text, above and blow, some characters appear bolded. Right now, the "t" in symptom in the line above looks more or less bolded. If I move the cursor to the top of this window, the "t" changes to normal ... and then back again when I continued typing here.
As you can see I'm having difficulty even describing what's going on. It isn't at all consistent, it appears to be system-linked and not application-specific, and it isn't serious -- just quite annoying. Shouldn't be happening!
Oh, no, I checked: It isn't a problem with my glasses <grin>.
Suggestions about how to describe this and where to look for solutions?
TIA,
Henry

Answer 1

Everyone:
Here is some more evidence:
1. I thought about the issue, and the distortion seems to follow the cursor in all cases, though sometimes the effect remains after the cursor has been moved away. So, maybe it's related to (drum roll) the cursor? What can I change about the cursor? Its size, in the Universal Access preference. Unfortunately, adjusting the cursor size to maximum and back to minimum has no effect. Oh, well, it was a good idea.
2. Why don't I post a screen-shot of the distortion somewhere? So I put Grab on timer and fooled with the cursor in this very window until the text above "...Universal Access..." appeared with its lower pixels missing, waited until the timer expired. But.... The screen shot DOES NOT SHOW THE PROBLEM. In three completely different trials, the text in the screen shot was flawless. Hmmm, that should be a very good clue for someone who understands how the screen is maintained in MacOS.
3. Right now I have two windows side-by-side mostly filling my screen. On the left, a large photo in Preview. On the right, the Main window of Entourage 2004. I bring Preview to the front and I move the cursor to the approximate horizontal center of Preview's toolbar, which is very near the top of the screen, and I move the cursor vertically towards the bottom of the screen. About half-way, I observe, well, a ripple running across the photo, no --wait-- across the entire screen. Where the ripple meets text (in the Entourage window at the right), it distorts more or less as I've already described. I think it is important that the problem occurs in all windows, not the frontmost. Oh, yes, I've moved this window down near the bottom of the screen and, so far, I've seen no problems. So the problem appears to only occur at mid-screen, vertically. That's where one usually works...
Ideas, anyone?
TIA
Henry