Check if your theme’s footer.php has the wp_footer() hook. If not add it to just before closing [/body]
I can’t believe it was that simple! Thank you so much.
Wish it had been as simple on my end. In BP site 1 the admin bar went missing right after upgrading to the latest BP version (footer hook is there, just checked). And on BP site 2 the admin bar is quirky. Some can’t see it, others can, settings stuff works for those who can, but login takes you to an error page. Admin options like mark user as spammer or delete user no longer work. Anybody else having these issues? Thanks.
We’re also having problems getting the admin bar to display. Anyone have any answers?!
thanks so much for this fix, sorted mine too 
Mine seems to be displaying — without css — below the footer. Anyone have a hint as to the cause of that? (Working on WP 3.0 nightly builds, using the Twentyten theme.)
What does the wp_footer() hook mean and where on the page should it go?
I have the same problem except that my theme has wp_footer() on footer.php
