We had the same (well, similar) thing happen. Screen froze up like a bar code.
I am very happy with them today because they stood behind their device and sent Hubby another one after we mailed our defective one in. He is happily reading again right now, and it seems faster and better in several ways than the one we bought at Borders last Christmas!
First - try their helpful hints and if that fails, email AND THEN CALL them. They were slow to answer our emails - but that first email will assign you the ticket number you will be using over and over, best to have it in print. They were wonderful on the phone (aside from the usual wait. Its a free number though!)
http://kobo.zendesk.com/home
HTH