I agree with Jan Morales.
I am running Gnome desktop 2.8.0 under FC3 and have installed thunderbird-1.0.2 from the RPM that came across the yum updater.
I tried installing the linc-1.0.3-3.1.i386.rpm and did a touch .autoreg in /usr/lib/thunderbird-1.0.2 and also in /usr/bin to no avail.
I am also getting the gray background for the mail message text portion of the window.
Dave