Just wondered if it might be a special Offers kindle. (That would make it fail)
AFAIK all devices are compatible with that modification. (NON-SO ones)
To change your custom screensavers, plug your Kindle to your computer via USB, and upload them to the linkss/screensavers folder that has been created by the hack. You'll have to restart your Kindle in order to take your new screensavers into account and prevent the framework from going crazy. To that effect, you can either use the autoreboot feature, or simply do a full restart of your Kindle.
so you did that then?