Chat messages are not delivered - dont even seem to reach DB

Hej,
I have just installed your chat plugin and while I can see both group-chat-windows and privat-chat-windows, including the avatars of the users, no messages are being delivered. I can type and send a message but it does not show up anywhere - I also checked the respective tables in the DB and this is what I found:
- wp_wpmudev_chat_users: entries for the chats are stored
- wp_wpmudev_chat_message: no entries
- wp_wpmudev_chat_log: no entries

I can see the ajax request being fired and I do not get any errors displayed...

I have the lastest release versions of WP (3.5.2), BuddyPress (1.7) and Chat (2.0.4) installed. Thank you for helping me out - I am excited to get this plugin working!!