Ok, have a Samsung 23" (SyncMaster 216 BW) flatscreen monitor (LCD?) I bought at 2007 Christmas? Anyway, about 10% of the time, it has a thin vertical yellow line, that's not from the computer signal, as I tried it with a totally different computer hardware/OS, and it still does it. But it's not "dead", and it went away today after I turned the monitor power off for a half hour.

Any ideas? Fixable? Exchangeable?

If you haven't tried yet you might change the cable to see if it's either the connections or the cable itself.

Nope, not the cable, changed that out.

Then again...I am using the old school cable with the multiple prongs, it's got a blue VGA connector with two screws on it...maybe I could try an alternate TYPE of cable...but the problem is intermittent, and I've used different cables, so I'm not terribly convinced that's the problem.

loose components inside, or worn/bulging capacitor can cause this problem,

as well as dirty power/surges. (is the power cord plugged into the wall directly or on a reputable brand surge protector?)

Hmm, could be power delivery...since after I turned the monitor off/on, the line was no longer there...

when i worked for walmart, i had to constantly explain to customers, that when they buy LCD HDTVs, that they should be plugged into a surge protector.

out of every 10 LCD TVs sold, 3 or 4 would come back, with the customer stating it would be discolored or have lines/dots on the screen.

all of them forgot to hook to the TV to a decent brand surge protector.

I had a couple of LCDs years ago that did this. Yes they were on a surge protector.

Started as a green vertical stripe as I recall, which would appear on seemingly random occasions. Exchanged it for an identical model, and this unit too started showing the green line (with a couple yellow) after a couple of weeks. Within a day or two, the entire screen was vertical colored lines. Tech support said it was dying (!).

So I returned it for another brand LCD, and was fine thereafter.

My neighbor had a plasma TV that had issues with a portion of the display intermittently showing a black stripe. It was never fixed, and eventually trashed. I did once see a guy YouTube fix this issue by hitting the screen and cabinet with a baseball bat, but I never mentioned that to my neighbor.

Just do a pixel massage at the very bottom of the line. If that doesn't work try it again at the top.

A WHAT?!

Put some plastic wrap over the screen (so you don't scratch it). Now press a pencil eraser up against the very bottom of the line and gently apply pressure while rocking the eraser back and forth.. like massaging the monitor. Be careful not to actually move the eraser just rock it back and forth.

Gradually apply more and more pressure until either the line disappears or until you aren't comfortable pressing any harder. If you have no luck with this try again at the very top of the line.

This method also sometimes works to fix dead (or stuck on) pixels hence the name "pixel massage"