Losing extended features in Reader when form is saved in 7 Stand

Hi. I have a form created in Acrobat 9 Pro with extend features in Reader enabled.

Procedure:
1) User1 with Acrobat 7 Standard opens the form, put in necessary info to form (form fields), do a "save as" then copies it to a server folder for User2 to add more info.
2) User2, with Acrobat Reader 9, opens up document, to add more info, e.g., name, etc.

Problem:
1) User2, with Acrobat Reader 9, cannot edit document anymore. Form fields are disabled, no info can be put it. It says "Document has been changed since it was created and use of extended features is no longer available."

It seems Acrobat 7 is disabling the extended feature and disabling form fields or making it as read only. However, User1 with Acrobat 8 Standard, can edit document and save in folder without giving User2 the extended feature problem or the editing part.

Is there a solution for this problem or a setting I need to do for Acrobat 7 Standard or is this an issue with Acrobat 7 since 7 does not have the extend features like Acrobat 8?

Any help would be much appreciated.

Thank you.