The icon is missing, not your PMs.
Please check your regular mailbox (at the curb) while waiting for us to fix this.
If you can't wait then click here: http://www.dnforum.com/private.php
Yes we upgraded to the latest release of vbulletins RC 1.
There are some template issues that we are resolving currently including some missing buttons etc.
Please report any issues you encounter here so we can rectify them.