An embedded YouTube video on a LiveJournal page doesn't display at all. Space seems to be allocated for the content, but nothing of it is shown. The same page behaves as expected in Firefox 2.0.12 and in the Safari packaged with MacOS 10.5 Leopard -- exhibits problem behavior in WebKit r30123 (10 February 2008).
I cannot confirm this bug.
Nor can I (r30123, 10.5).