You have a backup .PST file from a month ago, right?
Are the PST Folder Structure and Accounts the same now as they were a month ago?
If you do have a backup .PST file:
- Rename the current PW protected .PST file (add OLD to the file name)
- Copy (Restore) the month old .PST file backup to the same location as the current .PST file
- Open Outlook and see if it uses the month old file correctly