Try a manual reset.
Remove the rear snapback cover, and use the rest hole.
To remove the cover: a long the top edge of the bezel there is a bit of a cut out on one corner which gives you access to the edge of the snap cover, gently stick in a fingernail between the bezel and cover and lift the snapback away from the back of the reader, take it slow, the snapbacks have many little clips around the sides and in the middle to hold in place.
Once the snapback is off you will find the reset hole in the rear cover.
Kobo's instructions (Resetting device)
http://kobo.intelliresponse.com/answ...t+my+Kobo+Mini
(Removing back cover)
http://kobo.intelliresponse.com/answ....kobo.com/help