Fontexplorer X was in my login items, and as soon as I updated to 10.5.2, I got many issues with several applications, including the dock, which freezes when I try to open a stack/folder.
When I quit Fontexplorer X, everything is back to normal.
I hope they fix this soon: it's my favorite font manager.
Apple Mac OS X
Snow Leopard operating system.
Version: 10.6.2