Comment 69 for bug 1458593

(In reply to bugzilla from comment #63)
> This might not help, but I suddenly had this issue today out of the blue - I
> was prompted for my Google ID and Password, presumably to help synchronize
> my Gmail calendar with Thunderbird (not sure why it suddenly prompted,
> though) and then the 5-second pauses began. Made Thunderbird practically
> unusable.
>
> I managed to the Lightning extension, then restarted Thunderbird and all was
> fine.
>
> Then, something odd: I went into Thunderbird's "About" dialog and it tried
> to automatically update the program, but got stuck and never went beyond the
> "installing" message. My guess is that this was the case for months, as my
> version of TB was 26.x but the latest version turned out to be 31.1.2 when I
> manually checked on the Mozilla website.
>
> So, I downloaded the latest TB and installed over my current installation,
> then did likewise for the latest version of Lightning. Started TB and
> everything was working as expected, then installed the Provider for Google
> Calendar extension within TB and restarted. Integrated my Google Calendar
> back into Lightning via the new add-on (as opposed to using CalDev). UI
> performance is back to normal and my Google Calendar is properly integrated
> into the local Lightning view within Thunderbird.
>
> I realize this situation does not cover all issues mentioned within this
> bug, but hope it helps a bit.

Thanks <email address hidden>, that worked for me. :-)
My Thunderbird was version 24.6 (not sure about the .6, sorry) with an older version of Lightning; perhaps I'd disabled auto update and forgotten about it. When I manually updated Thunderbird to the current version (31.1.2) and allowed it to find compatible versions of the addons, the problem (same symptoms, slow loading since a few days ago, when Google asked for my login details) and with the new Thunderbird and addons running, the problem seems to be gone.
Hope your post brings relief to many other people. :-)
(Windows 7 32 bit, Intel core2 duo, 4gb RAM, generic system with Gigabyte MB, Kaspersky Internet Security 2015.)