Created an attachment (id=7410) [details]
Background color loss as initially observed

Using Thunderbird 3.1.10 (as provided by openSUSE 11.2), after QuickFolders
auto-upgraded from 3.7.3 to 3.8.1, the folder tabs lost their normal background
color, and retained only the font color (screenshot QF-381.blingless.png) and
the hover + dragging-into color effects.

I restored 3.7.3 (background colors were back immediately,
QF-373.blingisback.png) and ran the update again. On the *first* TB run (with
the update web pages shown), the background colors are still OK
(QF-381.firstrunok.png). Restart TB *again* and they're gone
(QF-381.secondrunblinglessagain.png).

Created an attachment (id=7411) [details]
Returned colors after falling back to 3.7.3

Created an attachment (id=7412) [details]
3.8.1 on the first TB run after the upgrade

(Sorry for the spam, but Bugzilla doesn't seem to have an option to upload
multiple attachments in a *single* update ... :-C )

Created an attachment (id=7413) [details]
Restarting TB *again* -> problem reappears

tricky one - I removed the old gradient colorings in order to be compatible
with the latest versions of Gecko (old gradients are deprecated since Gecko16)
in order to avoid log-spam.FOr older versions of Thunderbird, there is a CSS
file called qf_palette_legacy.css which is overlayed via chrome.manifest:

style chrome://quickfolders/content/overlay.xul            
chrome://quickfolders/content/qf_palette_legacy16.css
application={3550f703-e582-4d05-9a08-453d09bdfdc6} appversion<16.0
style chrome://quickfolders/content/options.xul            
chrome://quickfolders/content/qf_palette_legacy16.css
application={3550f703-e582-4d05-9a08-453d09bdfdc6} appversion<16.0

it is actually tied to appversion (as Tb<8 does not understand platformversion)
so it should be overloading these styles correctly.

Can you install DOM inspector and check which styles are applied to the tabs?
If you need more detailed information on how to do this, please email me
directtly then I can help you to set up troubleshooting.

Public update after communicating with Axel off-Bugzilla:

The trigger actually isn't how many times TB has been started, it's *how* it is
started (summary changed accordingly). Change something in the add-ons (like,
update QuickFolders) and hit the "Restart" button - the tab colors are there.
Do it with the usual "Exit" and startup - they're missing.

Debugging indicated that in the error case, the relevant CSS file doesn't get
loaded at all. Axel prepared a pre-3.8.2 "attaching" the CSS to a different
object and with that version, I cannot reproduce the effect anymore.

Created an attachment (id=7415) [details]
QuickFolders 3.8.2 prerelease 2

Here is a fix that worked for me and also Jochn, tested in an XP Virtual
Machine with Tb 3.1.20.

Tech Note:

Instead of applying the qf_palette_legacy16.css style sheet onto the
quickFolders overlay chrome://quickfolders/content/overlay.xul I apply it
directly to Thunderbirds main mail window:

style chrome://messenger/content/messenger.xul             
chrome://quickfolders/content/qf_palette_legacy16.css
application={3550f703-e582-4d05-9a08-453d09bdfdc6} appversion<16.0

made similar changes to SeaMonkey and Postbox - works in Postbox 3.0.6 but has
to be tested yet in SeaMonkey... please test as thoroughly as you can, in case
something else is broken...