Kay,

I have had this happen multiple times. Usually somthing is on the far reaches of the pasteboard like a stray text box. Try selecting all and see if anything highlights around the upper or lower edges of the document. Get rid of it then go into your InDesign menu>Preferences>Guides & Pasteboard and change the Margin to your desired increment.

There have been times when reusing a document repeatedly that I could not find the issue and had to start a new document and move everything over. If that is the case you can use the Opt.+ Page Up/Down key to quickly scroll through pages.

-Eric