We have a 27" TV. When it was turned on today there was a 6 inch black vertical line running the full length of the screen just off center.
Any suggestions?
Yup…buy a new HDTV. 
You’re gonna have to eventually anyway.
Seriously though, I’ve seen a couple of TVs do that in my lifetime and it’s not worth fixing. I brought the last one that did that to a TV repair place and the guy told me what the problem was (don’t remember exactly what) and that it would be cheaper to just buy a new TV.
I’m waiting for my two TVs to die so I"ll have an excuse to go HD. One is a 10 year old Sharp…the display keeps getting dimmer and dimmer but is still watchable. The TV in my bedroom is a 20+ year old Magnavox (pre-Phillips merger) that has a bunch of minor problems, but nothing quite enough to justify scrapping it.
Does it look like signal interference? That is: ghosting? The black bar could be from a 2nd signal/station.
Look for loose cables and such. Also misconnected cables. Is there a 2nd source like a VCR that could be “adding” to the signal?
Samsung / Sony / Something else?
CRT / DLP / LCD / WTF?
VCR / DVD / SAT / CPU?
Could be anything from a magic marker to magic mushrooms. 
It is an Insignia CRT (something like that, cheap TV anyway) and it is only a few years old.
The band cuts right through the image.
I haven’t checked for wiring problems (or magic marker).
Hmm.
An LCD could easily have physical problems that manifest as vertical bars, but I can’t think of any that would affect CRTs. (Those are normally horizontal or diagonal and more wavey).
I’d expect something to be wrong in an electronics sense somewhere… does that happen using cable / DVD / everything else? Do you have any alternate inputs (DVI, RCA, S-Video, etc) that you could test?