Same problem After the unit starts up, after a couple of minutes, the display goes blank with a vertical line. - the position of the line changes sometimes. I haven't used the unit much, but now it seems I won't be able to use it at all.

There's a trouble shooting guide here, you need to check for the presence of 24V when it goes blank, and trace back to where it's disappearing (I assume it is losing the 24v, if not you'll need to go through the installer setup or read on...
My first thought would be to check the wiring which has been touched last if it started doing that after you had coil replaced.
As an aside I'm not sure which model you have but if it has batteries you should replace them (I don't think it does have batteries but not seen a model iv so I'm unsure)

https://customer.honeywell.com/resources/techlit/TechLitDocuments/69-0000s/69-1410.pdf

sir, most probably the display strip have been get damaged, the only way to get it properly back is to send it to authorized nokia service center near you.

sir,
1. you must download a spyware or anti virus, and just run it,
2. if the problem did not correct, save your files, re-format your computer,
3. Thanks!

that the problem goes away when the pc heats up for a couple minutes would lead me to believe that the problem is a bad connection. in short driver issues and hardware failure rarely if ever fixes itself after 10 min of running, where a loose connection might tighten up as it expands in response to the` heat.

Well if the panel is bad it would not clear up in any situation, so its not the panel. most likely the t-con board or just poor connections inside. Julio Millenium TV in Las Vegas.

There could be 3 possible reasons for a vertical lines

1. Driver for graphics card needs to be updated
2. Grpahics card faulty
3. LCD problem

try connecting an external monitor and see if the display is also vertical on the monitor, if yes the problem is graphics card, if no, the problem is the LCD. Hope this helps

Accordingto Garmin, this problem can be fixed by disabling the WAAS feature in teh set up menu. There is an incompatibility between the old Garmin software and latest WAAS upgrades. Later software from Garmin is supposed to fix this problem.

Possible Solution found on google....

My old Garmin 162 chartplotter was mounted on the binnacle guard and served me
well for many years. Lately, it started getting very slow to refresh screens.
At times, it would shut down with only a black vertical line on the screen. On
our last cruise, the screen froze at a very critical moment. Too old to
repair, I bought a new Garmin 440, which I am very disappointed with, but
that's another story.
I read an article in the GoodOldBoat newsletter about the Department of Defense
making changes to the WAAS satellites that have caused problems in Garmin 72
and 76. Garmin's tech support recommended to turn the WAAS function off on
affected units. So I got out my old 162 and turned the WAAS off and it works
fine. To make sure it wasn't a fluke, I turned it off and on several times,
and it always slowed down with WAAS turned on. With it turned off, the
position error or accuracy, increases 1-2ft, not a big deal. I hooked the unit
up on my truck and drove around. Not a problem. Further reading indicates
that other brands of GPS are also having problems with the new WAAS
transmissions.
So if you are having problems with your GPS and it is new enough to have WAAS,
try to turn it off

I had the same problem (blank screen, vertical line). After speaking with Garmin, I was told to turn off the WAAS function. Disable it for now, because the WAAS signal, coming from the satellite, has changed, and Garmin has not yet published a remedy to correct this problem. A fix should be out in a software update, sometime in the future, hopefully. Just so you'll know, I also did a software update, to the latest version 4.0. The unit performs perfectly now, however, the accuracy is not quite as good, due to the lack of WAAS.

What you said does make sense. When you have your unit in simulator mode, the GPS receiver is turned off, so it is not receiving signals from the satellites. The strange signal from the WAAS satellite must be what has been messing things up. Good Luck!

Sounds like something is getting hot causing voltage loss or drive pulse loss to the vertical IC. Maybe you have a bad solder joint. Try tapping the circuit board around the vertical section. A capacitor could be heating and opening up. Stargazer Also you might try using circuit cooler spray and make the problem show up.