Crunchbang: Can't use simple-scan without administrator rights

I'm running the latest version of Crunchbang 64-bit on a Dell E5510 notebook.

Installing my printer and scanner worked fine - I just used an existing Ubuntu tutorial. However, scanning without starting Simple-Scan as sudo produces an error message. My main account is listed as part of the group scanner, according to the output of less /etc/group. To my limited knowledge, this should suffice, shouldn't it? What more steps are necessary in order to run simple-scan without sudo?

Thanks in advance.