Like I said, the icon for adding a Flowplayer is missing in QuickPress mode. See my screenshot. Probably just a minor issue. The missing icon seems to point at 'https://gewone.nl/wp-admin/RELATIVE_PATH/images/icon.png'. Oh. I have enforced SSL for my WordPress installation, perhaps the icon is there in straight http:// mode, I wouldn't know since I haven't bothered disabling SSL enforce just to see how it shows in http:// mode.