We have noticed an oddity in our local installation of Jira. If a user has rights to do so, and attempts to add a new project from the All Projects screen or the drop down dialog, we receive no response and Jira doesn't respond.

If you first login to the System Administrator panel first, then try the Add New Project from anywhere, it works. So, it seems like the dialog is set to fail if you don't have admin rights, but it never starts the challenge to request you enter your password again to confirm for temporary admin rights.