I don't actually have Thunderbird installed right now & don't normally even use Windows. ( IF OTHERS SEE THIS PROBLEM

1. Click the [I have this problem too button]
2. Start your own question using /questions/new/thunderbird/other
3. Comment in this thread but only
   To say you have started your own thread.
   Or if you have a solution to the problem }

If this is a problem one or two months old; whether due to a Windows or T.bird bug we probably would have seen a lot of posts about it.

• Is it only T.bird and not other programs that have this issue ?

The thread you mentioned /questions/987606 was started over a year ago and blamed on a Windows problem.

• Is your Windows software fully updated ?

Hibernation uses quite bit of disk space I suppose its just possible that may be part of the problem.

• Roughly how much free space is there in your HDD as percentage of the total
  • and in Gigabytes ?
  • and how many Gigabytes RAM memory do you have ?

John99 said

• Is it only T.bird and not other programs that have this issue ?

Yes, otherwise I would not report it as a Thunderbird issue.

• Is your Windows software fully updated ?

Yes.

Hibernation uses quite bit of disk space I suppose its just possible that may be part of the problem.

• Roughly how much free space is there in your HDD as percentage of the total
  • and in Gigabytes ?
  • and how many Gigabytes RAM memory do you have ?

725 GB free space (~75%). 8 GBs of RAM.

Do you still see this when starting Thunderbird in safe mode? https://support.mozilla.org/en-US/kb/safe-mode-thunderbird

Themes or addons may cause this sort of issue so worth trying T.bird's safemode as suggested by christ1

Of course ths problem is difficult to troubleshoot as apparently it is intermittent. You could also try Windows own safemode. The missing buttons are Windows components, and if you suspect it is related to hibernating try hibernating and starting again whilst in windows Safe mode. If you are able to find some method of

• Reliably or relatively reliably reproducing the problem it will become easier to investigate.
• OR Preventing the problem appearing.

Practical advice for a workaround

• The three bar menu button has an exit button.
• The old Windows keyboard shortcut Alt + Space still works on Windows 7.
  • Does that give you back control, when the buttons do not paint ?

P.S. Note that one feature of T.bird/Fx Safe Mode is that it turns off Hardware Acceleration.

Thanks for all your advice.

I don't have any themes installed but the standard. I didn't install any add-ons deliberately but some may have been installed by other apps.

I'll see if I can reproduce the problem consistently (although I don't think I'll succeed in that, I've seen no consistent pattern until now). First I'll be running TB in safe mode for some days and see if the problem occurs here.

One thing I have noticed is that the buttons are rendered differently in safe mode, like the bottom part is partially covered. Is that expected? Their behavior don't seem to be affected by this. Please see attached image.

Try disabling hardware acceleration and see if that helps.

see https://support.mozilla.org/en-US/questions/1012145

After a long time without running into this problem, it has now been present both today and yesterday while running Thunderbird in safe mode.

I'm now convinced that this issue is related to remotely connecting to my computer through RealVNC's software, because I did that both yesterday and today and I didn't do it for a few weeks before yesterday.

I cannot reproduce the issue consistently though. The only thing that I know RealVNC does when remotely connecting to my computer is switching to the Windows 7 Basic color scheme (a message in the system tray tells me that) and when I disconnect, W7 switches back to whatever the color scheme was before.

Now I'm convinced although I can't reproduce the issue on demand. I haven't had the problem for two weeks and today I once again made some remote connections to my machine through the RealVNC software (latest version) and the problem with Thunderbird has now occured again. I don't know the internal workings of RealVNC, but obviously it causes problems with Thunderbird. I haven't seen this issue with any other programs that I'm running.

None of your other program use XUL as a window definition language either is my guess. Are you using a non standard theme? Does this occur while in the VNC or only after the event?