Thank you for your post.
I cannot duplicate the problem. This is what I have done.
1. I created a database, Test.fp7 with a few fields and a few records.
2. I created a database, Test1.fp7, with a few fields and a few records.
3. I selected Test.fp7 and set the Orientation to Portrait.
4. I selected Test1.fp7 and set the Orientation to Landscape.
5. I selected Test.fp7, and the Orientation remains at Portrait.
5b. I changed the Orientation to Landscape.
6. I selected Test1.fp7 and changed the Orientation from Landscape to Portrait.
7. i selected Test.fp7, and the Orientation remains at Landscape.
I performed these steps with FileMaker Pro 10 on a Dell Dimension running Windows XP (sp3). If you can give me the exact steps you took, I will try and duplicate the problem.