When I try to boot any snapshot the following happens:

select snapshot xy
<enter>
new menu, asking whether to boot snapshot xy
<enter>
new menu, saying like "If everything works okay, enter "snapper rollback"
... nothing more happens. Pressing any key will not have any response, but
<ctrl><alt><del> will initialize a new boot sequence.

If one omits the second <enter> and waits out the preset delay, one gets a
black screen with some text like "Default as well as alternative entries could
not be booted (in German: "Sowohl die Vorgabe als auch die Alternativeintr�ge
konnten nicht gebootet werden.")

Is there any setting up needed to use snapper? Right now it is unaltered the
way it was installed.