Please describe the problem:
After upgrading from 2.2.5 to 2.2.6, creating a new invoice caused the wrong Open Date to be inserted.  Repeated attempts to change failed, the invoice does not show the new Open Date.  The search screen did show it as correct after edit however this date was not displayed or used anywhere else.

Steps to reproduce:
1. Create a new invoice.  Open Date defaults to start of the month (2008-08-01) - this never happened before, it has always been the current date.
2. Changed Open Date to today (2008-08-09) and filled out remaining info.
3. Opened invoice.  Date Opened shows as 2008-08-01 and is greyed out.
4. Clicked Edit Invoice, edited date.  Did not show as changed.
5. Closed invoice and searched.  Search showed correct date but opened invoice did not.
6. Repeated step 4.
7. Tried to Post invoice.  Post date was stuck on 2008-08-01.  Due Date was same despite having 15-day terms set.  Open date field was editable but always reverted to 2008-08-01.
8. Removed terms, repeated steps 4-7, same results, except this time Due Date was editable but also always reverted.
9. Closed and reopened GnuCash, repeated steps 4-7, same results.

Actual results:
See above.

Expected results:
Open date should default to today's date.  Editing this date should show on invoice.  Terms should be honoured when calculating Due Date.

Does this happen every time?
Unknown, did not try again as I did not wish to create another invoice to avoid messing up my books.

Other information:
Reverted back to 2.2.5, then was able to edit and post the existing invoice as expected.

Running on Windows Vista.