admin bar disappears completely in 2010 theme

And I found the solution via another unrelated admin bar question.

If anyone ever comes across this problem with the user_frontend plugin or any other plugin posting data from a custom form – apparently WP unchecks the two admin bar related check boxes if a set of data is sent to update the user profile that does not include the check box values. Accordingly, WP dutifully didn’t render the admin bar while I was logged in.

I’ve contacted the plugin author to look into this.