If you set up a layout in one page setup orientation and put objects in a place where they won't show up in a new orientation, then switch to the new orientation, the objects will not appear on screen since they are positioned outside the new viewable area of the page.
To see the issue:
1) Create a database file. Go to the layout and put the body label and a field below 9" on the vertical ruler.
2) Choose Page Setup from the File menu and change the orientation to Landscape (the rightmost option)
You will see that the body part label and the field have disappeared, and you will not be able to get them back by going to Insert Part or Insert Field. The solution is to change back to Portrait orientation, move the items back to where you would see them, then switch to Landscape.
This layout issue is caused by two aspects of ClarisWorks. First, database layouts are limited to one page, so you cannot scroll beyond the bottom of page 1. Second, ClarisWorks allows objects to extend beyond margins and page bounds. This can be quite nice for cropping an object, or splitting it across pages. However, switching to Landscape mode when you have a full-page Portrait database layout simply hides the layout parts and objects which are placed below the new shorter page boundary.