I just finished upgrading one of my sites to GL2.0.0. While using the "Upload a Plugin" feature to install the new Menu plugin I got the following error:
Fatal error: Call to a member function fetch_array() on a non-object in /home/mywebsite/system/databases/mysqli.class.php on line 653
I had to use phpMyAdmin to disable the plugin in the gl_plugins table.
It turns out that I had an old plugin also named Menu installed and when I did the upload it did not check to make sure a plugin with the same name wasn't already there.
I deleted the old menu files and removed all references to it in my database and was able to upload the plugin without any problems.