InfoPath 2007 Be aware of Its traps

I worked on an ordinary form for my customer in Infopath 2007. I updated the data source connection (Web Service) by saving the changes and closed the form, so infopath will be updated with the changes.
When I tried to open my form I get the next Error :

The form definition (.xsf) file contains elements, attributes, or structures that are not valid.

Error details:
The keyref 'RepeatingData_15' does not resolve to a key for the Identity Constraint '{http://schemas.microsoft.com/office/infopath/2003/solutionDefinition}xmlToEdit_name_key'.

Line 689, Position 5

----^

It took me one hour but I managed to reopen my form.
I solve it by:

• extracting the XSN file ( just change the xsn to cab, it's a regularly cab file)
  
• deleted any keref in the manifest.xsf file. (each time I reopen the form and get the same error but different keyref)
  

Infopath saves a temp refs in the form which after a while becomes junk that avoiding you to work on your form.
I suggest to save the form for each change and reopen it after the save.

I know it's sounds not so good but it's better than seating for a hour and editing xsf file by hand.