I don't know what's causing that. There's a huge long description on the page

https://addons.mozilla.org/firefox/addon/groupspeeddial/

but I think it only mentions that problem in the context of downgrading, not upgrading.

I didn't see an email address or forum for support, but to be honest, my eyes glazed over so I might have missed it.

Yes, the creator of the extension notes that this situation can happen in downgrading, but as you note, I am upgrading.

He does have a support page but is sparse. https://fastaddons.com/ Their is a email address at the page bottom for him. admin@fastaddons.com

Please let us know if this solved your issue or if need further assistance.

I did contact Juraj, and he indicated he thought Malwarebytes was involved with the problem. The next time I update FF, I plan on disabling Malwarebytes during the upgrade and see if that matters.

Can try this : uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) Then restart system. Then run Windows Disk Cleanup. (Note: This should be Pinned and run Weekly, If never done below expect 10's of gig's) Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Reinstall with Current Release Firefox 57.0.4 with a Full Version Installer

• https://www.mozilla.org/firefox/all/

Please let us know if this solved your issue or if need further assistance.