I've seen this behavior too, but I'm not sure what's causing it, and there doesn't seem to be a reliable way fixing it. In any case, your calendar and task data is not lost.

What I'd try: Determine your profile folder via Troubleshooting Information.

At the top right of the Thunderbird window, click the menu button , then select Help > Troubleshooting Information > Profile folder > Open Folder.

This will open the profile in Windows Explorer.

Close Thunderbird.

Temporarily stop your anti-virus real-time scanner.

Navigate to the extensions subfolder, and locate a folder {e2fda1a4-762b-4020-b5ad-a41df1933103}. It is the Lightning extension. Delete that folder.

If there is a 'staged' folder delete it as well.

Start Thunderbird, and install Lightning again. For Thunderbird 38.4.0 the corresponding version of Lightning is 4.0.4.1.

If it did work this time, turn anti-virus back on.

Hi, thanks for the reply.

My "extensions" folder doesnt appear to have that folder. It only contains: - folder "{847b3a00-7ab1-11d4-8f02-006008948af5}" - file "Extensions.rdf", content: a pretty bare bones xml file, only " <Seq about="urn:mozilla:extension:root"/>

 <Seq about="urn:mozilla:theme:root"/>" in there

- file "installed-extensions.txt", content: "theme,{972ce4c6-7e08-4474-a285-3208198ce6fd}"

Does that mean that actually, my tasks are wiped, or can they be somewhere else?

Anyway, it's back now!

I now tried installing it, with MS security essentials live protection temporarily off. I'm not entirely sure that was it, though. The other thing that was different was that, now it showed me again after selecting the plugin to install from within Tunderbird, quite a while after clicking "install", that "will be installed after restart". very little, in some little bar at the top. I clicked the button "restart now", which I might not have done before but closing thunderbird manually instead, and then waiting patiently staring at a blank desktop for maybe half a or an entire minute, to finally see thunderbird open again. I may not have been patient enough before and thought it didn't do anything, because there was no indication it was doing anything.

So, *perhaps* this could be something worthy improving, if in fact this had anything to do with it.

Thanks for your help!

Good. When your problem is fixed, can you mark the thread as 'Solved' please? Thank you.

I also do not have the folder {e2fda1a4-762b-4020-b5ad-a41df1933103} and still cannot complete the install.

I am seeing that Thunderbird does not have access to write to the necessary file but it does not say what the file is or what folder it is in. I have tried in Adminstrator account also with all anti-virus disabled and it still cannot write to the necessary file. Hope this sheds some light on this issue.

lanmanager,

you're responding to a thread which has been marked as 'Solved'. If you still have a problem please start a new thread for your problem. Provide as many details as possible.

Christ1 - Genius!

I tried so many times to install Lightning with no success. By following the above, even though the file you suggested wasn't there, the process has worked. Thank goodness I now have my calendar with all its entries back again. THANK YOU SO MUCH!

SueRit,

I tried so many times to install Lightning with no success. By following the above, even though the file you suggested wasn't there, the process has worked. Thank goodness I now have my calendar with all its entries back again. THANK YOU SO MUCH!

It would be great if you could post your reply above to your OP at https://support.mozilla.org/en-US/questions/1102845 and mark your OP as 'Solved'. Thank you.