We can surely help with restoring your CheckBook Pro data, but we'll want to gather some additional information to determine what might've happened there to make your Accounts file inaccessible and how best to proceed. Rest assured that the application saves Backups about once a week, so there are definitely options.
Anyway, can you send the following in an email to us at
support@splasm.com?
1. A System Information report. This report tells us how your Mac is configured. You can create one of these reports by clicking the Finder icon in your Dock, going to the Go menu at the top of your screen, clicking the Utilities menu item, opening System Information.app, then going to the File menu and clicking the Save... menu item.
2. Your recent system.log files. These files contain routine status messages from apps, but they also contain any error messages these apps may have logged, in addition to any error messages the Mac itself may have logged. We need to see these to get an accurate picture of whether some major issue occurred and, if so, to explain why. You can find these by clicking the Finder icon in your Dock, going to the Go menu at the top of your screen, clicking the Go to Folder... menu item, pasting "/var/log” (without the quotes) into the Go-to-folder field, and hitting Go. Send every file in that log folder whose name begins with the word "system”.
Thanks for working with us on this! Once we receive your email, we should be able to get right back to you with a plan.