stas123 posted a fix/workaround in the form of a modified MessagingWidgetsSMSConversation.js for US owners. A few months back I modified it slightly so that it'd work with those set with a canadian...
If you used Mass Storage mode, then you did not read and follow the guide in the first post correctly. It directs you to use your local network and winscp to send the files and not a usb connection.
ZogG was completely correct. Without the patched version, this exact issue happens where the game on the XMB is not changed to the one you selected in the Backup Manager.