I'm not sure that I understand what I am looking at in your layout.
Do you have two container fields on this layout where you've inserted a PDF file?
What does this layout look like in layout mode?
Let me clarify for you. This is a database with which I have created using the Tab Control Tool. The data has been transferred/migrated into the Tabs. As per the content there are three Tabs: General, Payment and PDF. On the General tab, general information such as First/Last Name, Rental Fee, Lease Duration, Date Signed and Notes is to be displayed. On the Payment tab, there is payment related information such as Lease Value, Lease Value, AgreementID and a Portal to another table named Payment displaying Date Paid, Payment Amount, AgreementID is to be displayed. On the PDF tab, there is Lease Document information with a Container field for storing the .PDF Lease Agreement document or a refernce to it by way of a Quicktime file. This is how the layout is supposed to display in Browse mode. When viewing in Layout mode, everything displays fine on each of the three tabs displayed. For some strange reason when I switched the Page Layout from Portrait to Landscape mode the contents of what is displayed on the PDF and Payment tabs has somehow bled through onto the General tab. This is what you are seeing in the screenshot. I also would like to know when in layout mode, what this thick black vertical/horizontal set of lines denote? Are these the margins for when printing? To get the body of the database to display correctly the Tab layout extends outside the thick black vertical/horizontal set of lines. Is this also a problem? I do not intend to print out the database but margins always have to be taken into account, right? I mainly am creating a solution that will display the database in a confined space such as small monitor, iPod Touch, iPhone and iPad. Hope this clarifies the confusion.
If the layout will not be printed, you can ignore the horizontal and vertical lines you describe as they only tell you where the page breaks will occur should you print this layout. I also find it unlikely that a change in page orientation had any effect here as that also only affects the position of these lines and what you will see when you enter preview mode.
I'd guess that your entire tab control is a few pixels too high on the layout and that the upper edge of the control either touches or crosses the boudnary between the header and the body. Move the entire control down a pixel or two until it no longer touches or crosses this line and you should see the correct appearance when in Browse mode.