I've just upgraded two websites of mine brandasy.com and restaurants-uncut.com to the new version 2.9.1. While brandasy.com is working alright, in restaurants-uncut.com, the add media buttons are not working whereas in the status bar at the bottom, it is showing the message 'errors on page'.
What can be the problem. Why did one upgrade go perfectly alright while there are problems in the other. I used the same wordpress to upgrade both websites and followed all the steps including disabling plugins before the upgrade.
What can I do to resolve this media upload issue?