bad PNGs, thunderbird and firefox

[brian]

thunderbird-3.0-2.6.b3.fc11.i586
firefox-3.5.2-2.fc11.i586

Suddenly, most of the icons in thunderbird and *some* images in ff are 
pretty messed up. They appear to be indexed to just 3 colours. 
Sometimes, it's predominantly neon green, other times purple or black. 
In TB, it's the ones that are highlighted, except for folders, which 
look fine. Any icon that's greyed out also appears normal. Also, the 
icons in the "write" window i'm typing now in are ok.

In FF, there doesn't appear to be any rhyme or reason, save for the fact 
they're all PNGs. I thought that it was background images only, but that 
doesn't appear to be the case. Nor are all PNGs screwed up.

I recently installed an LCD display and so modified my xorg.conf. But 
this problem only just appeared so i doubt it's related. Is anyone else 
seeing something similar (it's *really* hard to miss).

Otherwise, can anyone think of what I can check?

Here's the latest from yum.log:

Aug 19 16:40:07 Updated: gvfs-1.2.3-11.fc11.i586
Aug 19 16:40:07 Updated: pciutils-libs-3.1.3-1.fc11.i586
Aug 19 16:40:08 Updated: nss-softokn-freebl-3.12.3.99.3-2.11.4.fc11.i586
Aug 19 16:40:09 Updated: nss-3.12.3.99.3-2.11.4.fc11.i586
Aug 19 16:40:09 Updated: pciutils-3.1.3-1.fc11.i586
Aug 19 16:40:10 Updated: libmtp-0.3.7-2.fc11.i586
Aug 19 16:40:12 Updated: nss-tools-3.12.3.99.3-2.11.4.fc11.i586
Aug 19 16:40:12 Updated: gvfs-smb-1.2.3-11.fc11.i586
Aug 19 16:40:12 Updated: gvfs-obexftp-1.2.3-11.fc11.i586
Aug 19 16:40:13 Updated: gvfs-archive-1.2.3-11.fc11.i586
Aug 19 16:40:13 Updated: gvfs-gphoto2-1.2.3-11.fc11.i586
Aug 19 16:40:13 Updated: gvfs-fuse-1.2.3-11.fc11.i586
Aug 19 16:40:17 Updated: gdb-6.8.50.20090302-37.fc11.i586
Aug 19 16:40:53 Updated: gnome-settings-daemon-2.26.1-8.fc11.i586
Aug 19 16:41:06 Updated: 7:squid-3.0.STABLE18-1.fc11.i586
Aug 19 16:41:06 Updated: m17n-db-1.5.5-1.fc11.noarch
Aug 19 16:41:07 Updated: kernel-firmware-2.6.29.6-217.2.8.fc11.noarch
Aug 19 16:41:08 Updated: pciutils-devel-3.1.3-1.fc11.i586
Aug 19 16:41:10 Updated: nss-devel-3.12.3.99.3-2.11.4.fc11.i586
Aug 19 16:41:15 Updated: setroubleshoot-plugins-2.0.18-5.fc11.noarch
Aug 19 16:41:19 Updated: kernel-headers-2.6.29.6-217.2.8.fc11.i586
Aug 19 16:41:47 Installed: kernel-2.6.29.6-217.2.8.fc11.i586
Aug 19 16:41:47 Updated: systemtap-runtime-0.9.9-3.fc11.i586
Aug 19 16:41:52 Updated: systemtap-0.9.9-3.fc11.i586
Aug 19 16:41:53 Updated: m17n-lib-1.5.5-1.fc11.i586