GM --
When you launch Microsoft Project Professional and log into Project Server,
and then click File - Open, you automatically see the Open from Microsoft
Office Project Server dialog. If you click File - Open and see the Open
dialog (used for saving the project as an .mpp file), then this indicates
you are not logging into Project Server so that you can work in enterprise
mode. Therefore, you must create a Project Server login account in
Microsoft Project Professional by completing all of the steps in the
following link:
http://www.projectserverexperts.com/Shared Documents/CreatePMLoginAccount.htm
If you had already completed the steps referenced above, and you are logging
into Project Server with Microsoft Project Professional, then your situation
would probably indicate that your Project Server administrator has set the
Open Project permission to Deny for the My Organization category in the
Project Managers group in PWA. Ask him/her to check this.
Let us know if any of this helps your situation.