Please, remember that if you are having issues with Next Gen JMC after an update, please empty the cache on your browser first to see if that clears them up. Most of the time, that will take care of the issue. The instructions are below:
For Internet Explorer, go to the upper right side to the Tools pull-down menu, and go down to Internet Options. In the middle of your screen, click on the Delete button, and at the next screen, make sure that Preserve Favorites Website Data is unchecked in the top section. Then make sure Temporary Internet Files, Cookies and History are the only ones checked in the bottom section, and then click on Delete. Once it is done deleting all these temp files, etc., quit out of Internet Explorer, and then start it up again, and log back into your JMC.
For FireFox, just go to Preferences or Tools:Options, depending on if you are using a Mac or Windows computer, and go to Advanced:Network. I would set the Cache to 0 and then click on Clear Now. You can also go to the Privacy section, and check the box in front of Clear History When FireFox Closes. Then click on the Settings button to the right of that, and check the box in front of Cookies and Cache, and click OK. Then log out of JMC and quit FireFox, and then go back in.
For Chrome, go to Settings, and then click on Show Advanced Settings at the bottom. Then in the Privacy section, click on Clear Browsing Data, and check the top 4 boxes, and choose from The Beginning of Time from the pull-down menu, and then click on the Clear Browsing Data button at the bottom. Then log out and quit Chrome, and go back in.
For the old version of Safari (version 5), just go up to the Safari menu at the top left, and highlight Empty Cache. Then log out and quit Safari, and and go back in.
For the new Safari (version 6), Empty Cache is no longer in the Safari menu, so go to Safari:Preferences:Advanced. At the bottom of that window, check the box in front of "Show Develop Menu in Menu Bar". Now get out of Preferences, and go to the Develop Menu at the top, and click on Empty Cache that is in this new Develop menu. Then log out and quit Safari, and go back in.