1. The Thunderbird app is on one display. When it is open to the mail tab, no problem. When it is open in the calendar or task tab it will leap across both displays. I have to go back to the mail tab to get that cleaned up. (this is approximate, but I'm putting it aside for the moment to work on the more important things and don't want to research it more deeply yet.)

2. Going through the rest of your steps. Hey, that previous problem is fixed now! Back to the beginning of my request. I cannot add a task or event. I now have a "Home" calendar, but cannot see it in the calendar tab. In the calendar tab, in the lower section, is "Day," "Week," "Multiweek," and "Month" tabs. However, they are dimmed and nothing happens when I click them (obviously, or should be obvious, but I've known times when...)

Any more help would be appreciated, but thank you for getting rid of the annoying flicker. :-D Dunno how to add "new problem came up and got fixed somehow" on your record.  :-)

I killed lightning again but this time I installed from file. 1. Now I CAN access the calendar! So somehow something solved that. 2. However, the flickering has started again.

It seems that installing from the file causes the flickering!?

Anyway, the calendar is there and maybe the calendar will be useful, but I don't think it would be very usable if I get an epileptic seizure. Not that I've ever had one--but this problem makes me feel like I"m getting dizzy.

Should I mark this as "solved" and open a new thread on the flickering?

The thread is long, but I don't really care for the one question one thread policy. I figure you got a problem and someones ear. Bash it.

Having said that I am not sure I have all that much to contribute. I have heard that Windows clear type can cause all sorts of issue. Perhaps try disabling that in windows

See http://www.thewindowsclub.com/disable-font-smoothing-windows

Thanks for your patience, Matt.

Well, I killed cleartype (can you see how bad this looks now? :-D ) but the flickering problem remains. Worse, I pulled in that calendar I had backed up and, though it still exists, the "Home" calendar has disappeared. So I'm back to square one on that, too.

I figure that I can solve the flickering problem by going back to using one monitor but there is one problem: this is a work computer.

I'm using Windows 7 and have been waiting for excitement (of any potential gotchas) to die down for Windows 10 before broaching that subject to my boss. Any idea if not updating could be part of the problem.

I use Thunderbird on Windows 7 pro 64bit (I just never cottoned onto 8) I also use in on a dual monitor setup. with the desktop stretched across the two.

The biggest difference I can see is you have a couple of different add-ons and I have an AMD Radeon HD 7500 video adapter with 1GB of ram.

I forget, but have you checked the Nvida web site for a driver update. See http://www.nvidia.com/Download/Scan.aspx?lang=en-us

The link wasn't as helpful as the concept. It led me on a merry chase to install the newest Java and then told me that I have a notebook...! lol. So I checked the drivers out in a different way. Drivers are up-to-date.

Good idea, though. Thanks.

I took the other adds-on off early in the game and that didn't help, but that was another good idea. Again, thank you.

I never really cottoned to gui anything and still happily use console applications. :-0