If you upgrade wxBanker and find you run into issues, you can restore the backup that wxBanker automatically creates before each upgrade.
Also, pretty please file a bug at https://bugs.launchpad.net/wxbanker/+filebug so I can fix it for you and anyone else experiencing it. Your current bank file is stored likely in ~/.local/share/wxbanker/bank.db on Linux, ~/.wxbanker/bank.db on OSX, or in the same directory as the source files on Windows.
In this same directory you will also find the backups with a name such as "bank.db.backup-v10-2010-03-28", the version (in this case "v10") refers not to the wxBanker version but the internal database version, so you'll likely want the latest one, likely with the date of your wxBanker upgrade. Simply delete the current bank.db, and copy the backup (so you can restore again if you needed to for some reason) to "bank.db". Now just make sure to also revert wxBanker itself to the previous version.
