Please provide more details. What happens when you try to download or navigate away; do you get an error message or warrning dialog? If so, screenshots would help, as would the url of your Express file (from the browser's address bar when the file is open).
Thanks for you fast reply! This is the message I get when I try to download any file or try to share it: [cid:image001.png@01DA1D26.0C6D3FA0]This also happens with new files I just now created.