I just upgraded from 1.5 to 1.6. On my test site it works fine. I brought it up on my production site, and the store appears to work fine. When I go to admin area and navigate to products, categories or topics, I can see the list for each. But when I click on one, the system displays a blank page. The master page structure is there (menu, header), and the save and delete button is visible, but the catagory portion is blank. It does not even display the field areas.
I also tried to add a category, and again not even the field areas were visible.
I also uploaded a copy of catagory.aspx directly from my test site where it is working. No change.
I used the same build for my test site and my production.
Any ideas?