Hi I know there are quite a few people who have purchased the elonex 621eb who have had to return their product after it has frozen.
Here is the fix supplied bu Elonex, it works I discovered this after my second return, it is a firmware update. Just a quick note you will loose your stored books but at least you'll have a working reader. Here it is.
To complete the firmware upgrade for the 621EB please follow the steps below. In the vast majority of cases there is no need to perform this upgrade so it is recommended that you only complete the upgrade after being instructed to do so by our Technical Support Helpdesk.
PLEASE NOTE: A 2GB SD Card or larger is required for this firmware upgrade.
Step 1: Insert an empty SD Card into your computer and format the card to the FAT32 file system.
Step 2: Download the firmware file here to your SD Card.
Step 3: Unzip the firmware files into the SD Card. It will take about 15 minutes to do this step.
Step 4: Insert the SD card into the SD slot of the 621EB.
Step 5: Connect a source of power either from PC or from mains.
Step 6: Press the “Return” button, “Enter” button and the Reset button for 5 seconds. (The “Return” button is the third button on the left hand side of the eBook, and the Reset button, found on the rear of the unit, should be pressed with a paper clip).
Then release reset but still holding down the two other buttons. Keep holding the two buttons till the screen counts up 6 squares and then shows a new firmware screen. Once firmware screen pops up release buttons.
Step 7: The unit will then reboot and count up the 6 squares and then will jump into the firmware upgrade.