Since you appear to be using Windows 8.1 64-bit and Thunderbird is 32-bit, did you make sure to
- Remove both Thunderbird folders in C:\Program Files (x86)\ AND C:\Program Files\ if they both exist? - Perform the new install in C:\Program Files (x86)\ only?

Tonnes said

Since you appear to be using Windows 8.1 64-bit and Thunderbird is 32-bit, did you make sure to
- Remove both Thunderbird folders in C:\Program Files (x86)\ AND C:\Program Files\ if they both exist? - Perform the new install in C:\Program Files (x86)\ only?

Thanks for the reply :) There was no copy of the file in \Program Files, only \Program Files (x86) and the new install was in the (x86) only. I've just checked to confirm.

Try removing the content of the C:\Users\<username>\AppData\Local\Thunderbird\Profiles\xxxxxxxx.default\Cache\ folder and retry.

It could do no harm removing the entire content of the Local\Thunderbird\Profiles folder (or moving it elsewhere, just in case), as Thunderbird may be looking for another profile folder if you have set up more profiles - the above belongs to the profile assuming there is only one. Also make sure to choose the Local subfolder, which is the cache. The one with Roaming is the actual profile folder containing all email and settings and should NOT be deleted. (While at it, this is a good time to back that actual profile up.)

Same error unfortunately, I can't think what it is looking for and why its not simply installed with the fresh install. I noted that the folder wall called cache2, including in the new install. I renamed it to just Cache in case it fixed it but no dice. There are also no other profiles and backed up the profile data, thanks for telling me where that hides!

Actually there could be both a Cache and a cache2 folder. Since profile folders and their cache folders (in Local) are left untouched after uninstall, they could cause those install errors in some cases. Renaming cache2 to Cache and then removing Cache (if I got that right) would probably make no sense. ;) Removing the entire Local\Thunderbird\Profiles folder (i.e. all its subfolders) would be better, but I’m afraid this is not the cause for your issue.

Do you happen to run any antivirus software, perhaps Avast or Norton? If so, try switching it off and reboot, or even uninstall it entirely before rebooting. But before you do, make sure it contains no quarantained Mozilla items, or restore them in that case.

You might be able to check or add some exceptions in that software for Mozilla products while at it, though I would save that for last if the above helped and reinstalling/re-enabling it brings back the issue. Of course you could decide to install Thunderbird first and reinstall/re-enable the security software afterwards, but that may not solve it entirely - the issue may occur again at a next update or install.

Sorry for the delay replying; unfortunately none of the above worked. I've totally disabled antivirus and checked quarantines but no joy. I really can't see why it wouldn't, surely a simple clean install after all files have been removed would fix problems on a program that was working fine beforehand?

Try uninstalling Thunderbird and then removing the entire content of C:\Users\<username>\AppData\Local\Thunderbird\. That folder may contain cached installer files.

Then make sure to have downloaded the Thunderbird installer from here, not from any other source, and install it.

If that doesn’t help, download a zipped version of Thunderbird Nightly from here, unzip it in any folder and run thunderbird.exe from there as a test. I’d be curious to see what that does.

Hi Tonnes,

Thanks for your reply, the lateness of my reply is due to the fact that now Firefox won't work for me due to a 0xc0000022 error which, frankly, is not worth the several hours I've now spent trying to fix it. Sorry Mozzilla but two seemingly unfixable programs in a row is my limit. It was nice knowing you and when you worked you were great but I'm switching to Crome.

Too bad, but we’ll probably see you back. ;)

For the sake of others, most likely, one probably needs to totally uninstall AVG (or other securiy software) and reboot (NOT only just switch it off), then reinstall its latest version or a better security product if needed. Either that, or fix Windows - you may run into issues with other applications too.