I just installed a fresh jenkins 2.6. from the debian package repo and set it up with the default plugins for a start. When I create my first freestyle project, I see the fancy overlay with the loading animation, which does not go away. Upon first load of the configure page, the following two javascript errors appear in Chrome Version 50.0.2661.102 (64-bit):

Cannot read property 'firstChild' of undefined

in hudson-behavior.js:417

Cannot read property 'clickEvent' of null

in select.js:188

In Safari Version 9.1.1 (11601.6.17), apparently only the second error in select.js pops up in the console.

See attached screenshot.
The server-side log does not show any exceptions.

Steps to reproduce:

• Grab an arbitrary ubuntu 14.04 server box
• Add deb http://ppa.launchpad.net/webupd8team/java/ubuntu trusty main package src and accompanying key
• run sudo apt-get update && sudo apt-get install oracle-java8-installer
• Add deb http://pkg.jenkins-ci.org/debian binary/ package src and accompanying key
• run sudo apt-get update && sudo apt-get install jenkins
• Walk through setup process (create first user, ... ) and select "suggested plugins"
• Create a new Freestyle Project, and...
• As soon as you hit the /configure page, watch the nice loading animation forever...

Some more details:

$ dpkg -l | grep -e jenkins -e oracle
ii  jenkins                               2.6                                  all          continuous integration system
ii  oracle-java8-installer                8u92+8u91arm-2~really8u91~webupd8~0  all          Oracle Java(TM) Development Kit (JDK) 8
$ apt-cache policy jenkins
jenkins:
  Installed: 2.6
  Candidate: 2.6
  Version table:
 *** 2.6 0
        500 http://pkg.jenkins-ci.org/debian/ binary/ Packages
        100 /var/lib/dpkg/status
$ cat /etc/issue
Ubuntu 14.04.2 LTS \n \l

$