I'm forwarding this issue https://boxcryptor.desk.com/customer/portal/questions/1010543-file-open-and-save-error- here because it's something that must be addressed ASAP!
Me too I had to revert back to the previous public version on a Windows XP!
Build 154 has a problem when re-opening files on Windows XP in certain circumstances. Please download and install the new version where it is fixed:
Yes, it has solved my problem! Thank you!