Registered users logging into My Nero can see that 7.7.5.1 has been released. However, the file is listed at 0 bytes and can't be downloaded, as of this post.
Why non-registered users get access to newer updates and trial versions before registered users do remains a mystery to me:
http://www.nero.com/nero7/enu/nero7-up.php
In my opinion, Nero, with respect to new updates, is treating its registered customer base very poorly.