I know you mentioned already doing this, but it may help to go over the information in the below thread (by Patricia) and then check the information in the wiki link that it gives. I hope this helps.
https://www.mobileread.com/forums/showthread.php?t=21337
***a quick question...Do you have any pdf files on the Reader? Sometimes large pdf files get stuck loading or a large amount of pdf files cause my reader to take forever to load. I've had to delete those files and then my Reader is able to start up.***