I didn't ask the Amazon support team.
After reading the answer of a reboot. ... I just realised that i had duokan installed on my kindle.
I deleted it and restarted.
I can now open all my books without having to reformat everything.
I copied the folders of duokan back and evrything is back in order.
Thank for the hint geekmaster and ixtab ... i overlooked the dual boot. Sorry about that.
Last edited by pportnawak; 07-29-2012 at 10:01 AM.