@georgengelmann that's weird, most of the times AMD cards are the troublesome. If possible try the netinstall, or check h-node.org, in the Search page you can fill the out put of the terminal and search for reviews on the hardware if someone has tested it before.
In case there no info about your card, it would help us to know more details on it.
I can help you in real time using the official Trisquel IRC or the unofficial Matrix one
Cheers!