Thanks to @kunschj and @daveks for all your help and expertise. I am so happy to report that my 500 Steem was returned to my wallet this morning and I swiftly moved it to Bittrex! At least I have had loads of practice moving Steem to Bittrex, as I did it in 9 separate moves. LOL! The explanation I got with the returned Steem was that the system was being updated! Yay! I'm a happy camper today!