After upgrading to Toad 10.1.1 and I open my ER Diagram Model file, I get error: "Cannot open the (4309006)

After upgrading to Toad for Oracle 10.1.1.8 and when I try to load my ER Diagram Model .ERX file via Database Menu | Reports | ER Diagram, I get the error below.

ERROR:

Cannot open the selected Model. The file "C:\Users\<your_user>\AppData\Roaming\Quest Software\Toad for Oracle\10.0\User Files\ERDiagrams\ERD_01.erx" has unknown content.

RESOLUTION 1: 

Upgrade to Toad for Oracle 10.5.0 as this release has an automatic repair feature.

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RESOLUTION 2:

Open your  .ERX  in Toad for Oracle 10.5 and it should open, however you wil get the error below.

Error:
There were errors during loading the diagram.
The automatic repair feature was used, the diagram is not complete.

Re-save it with a new file name and this new file should now open fine in Toad 10.1.1 as well, without any errors.