Install 10.5.

You could try downgrading Safari. I Googled a bit and it seems like people have gotten the same problem quite a lot. Unfortunately it seems that each person fixed it differently. Try rebooting, disabling RSS, reapplying the update, applying <a href="http://www.apple.com/support/downloads/macosx10411comboupdateppc.html">this</a> update (if that's not what you already did and if you have a PPC processor ) or disabling/uninstalling PicLens.

Yeah, install 10.5.