OP is right. Something changed with the latest release of Leopard Webkit that broke linking fluid-apps to its updated framework. I think the last version that worked for me was 600.7.7, but i can't be sure.
I ended up getting around the problem by running the "system wide" installer for 600.8.10_2 (make a backup before doing this!). Fluid apps worked after that and it had the added benefit of speeding up the iTunes store browsing speed.