I've been using the Safari 4 beta for a while, but mostly what I've been doing is making straight photo posts.
So I thought I broke something when I went to add a link and everything broke.
The way Wordpress 2.7 does links is it pops up a lightbox and you type your link info there.
Well, the grey overlay pops up, and the link box tries to pop up, but it gets buried under the gray overlay, and there's no way to get out of it.
There's been lots of complaining, but there is a solution, posted here.