3.5 issues

http://wordpress.org/support/topic/troubleshooting-wordpress-35-master-list?replies=4

When you create a post, save it as a concept first, after that you might be able to use the media button and the switch between html and wysiwyg editor again. It is a work around but it works, at least it does for me.
To flush a caching plugin depends on the plugin. If you use wp-cache, go to plugin settings and under the tab content click ‘delete cache’. any other caching plugin must have the same functionality.