Running XP Pro with EZ Armor firewall I can't see any of the thumbnails attached to posts unless I turn off the firewall.
I've been playing around changing settings in the firewall but so far I haven't figured out what to change.
I hate to keep the firewall shutdown.

Anyone have any ideas?

Are you saying the small graphic doesn't display within the thread or the large version won't display if you click on the thumbnail?

The former might be some web optimizer setting to increase speed of downloads.
If it's the later it sounds like some type of pop-up blocker enabled.

Only the words "Attached Thumbnail" show.
If I turn off the firewall the thumbnail shows up normal and expands like it should if clicked on.

I'm out of ideas. The CA knowledge base is pretty weak.
You may get some help here with their online support chat area.
http://cahelp.web.stream.com/index.cfm?SVC=516

Have you tried XP Pro Service Pack 2? The pop-up blocker in SP2 can be customized to allow popups from specific URLs or turned off altogether. Maybe EZ Armor has such an option to list URLs it will allow.