Unable to save Estimates or Opportunities using the Standard Forms for a specific Subsidiary (getting unexpected error message)

If an administrator gets an Unexpected Error message when saving an Estimate or Opportunity using the standard form for a specific subsidiary, the following steps resolve the error:

Check the accounts:

1. Navigate to Lists > Accounting > Accounts
2. Look for account name : Opportunities and Estimates (both accounts are Non Posting types)
3. Edit the accounts
4. In the Subsidiaries multi-select field, check the subsidiaries that are highlighted.
Most likely the subsidiary with the issue is not highlighted in this field. Highlight the subsidiary and save the account.