Ron, it is an issue with the configuration. Specifically, Safari has a problem with the re-size-image modification that was added to the board. Before this was installed the board's layout would break whenever someone posted a relatively large image. I think perhaps that posters here are more prone to post larger images than those of railroad.net. I also think that hi-res images are a feature that most people really like about posts here. So, unable to find a better solution, I made a trade-off -- and one that Ive never really been particularly happy about, since I also own a Mac.
There is a very simple workaround, however. Just use firefox. I realize that many of the Apple faithful may find the idea of ditching Safari a bit sacrilegious, but what can I say? When the board switches over to VBulletin the issue will be put to rest for good.