Newsletter gets created but will only send a test email

Hi,

When I create a newsletter and send it to a test address this works fine, it shows up in the log's and i receive it the way it should.

But, when I try to send the newsletter i get the message "Newsletter created" and "newsletter being sent" but in fact not a single one gets sent.
Also none of many newsletters I tried to send show up in the newsletter list. But they do show up in the content list of the website.
(now I think about it I'm having that problem with audio too)

These are the last modules I need to set up for a client before I can let them go ahead with it, so I'm dying for some help.

Thanks in advance!!