OT?: Thunderbird/Firefox - http links changed to file: links??

[G.Wolfe Woodbury]

Recently Ive had a problem with thunderbird and firefox wherein an
http:://  link gets changed to a file:/// link somewhere between
clicking the link in thunderbird and the link opening in Firefox.

I've prowled through the advanced config controls of both apps and see
no obvious transformations.  I've disabled all extensions in Firefox
(especially NoScript) but the problem persists.  I've even uninstalled
and re-installed Firefox to see if that helps.

The next step would be to remove my personal .mozilla tree, but this
would mean loosing all my settings and I've worked a lot customizing my
preferences that I'd rather not lose.

I've done some superficial google searches for the problem, as well as
the Mozilla bugzilla with no relevant returns, bu I admit my google-fu
may be inadequate.

So, has anyone seen anything like this?  Were you able to cure it?

Thanks for any help offered.

Fedora relevance: it happens on my F10 installation, not F9 nor the
EvilEmpire installations.