An important concept to understand in Stardraw is the Document Boundary. Stardraw supports, effectively, an infinitely-sized drawing area, which can cause issues with Windows scrollbars, for example, if you move the scrollbar thumb halfway to the top, i.e. halfway to infinity, where should the view on the document go? (You can't calculate half of infinity) The Document Boundary is there to allow the scrollbars to work. By default it is not shown, but you can display it using View | Boundary (or typing VB). The scrollbars allow you to move approx 100% to the left or right, bottom or top of the Document Boundary.
If your drawing starts to get a lot bigger than the Document Boundary you may find that the scrollbars 'seize up' - this sounds rather like the effect you described - and you should resize the Document Boundary to fit the drawing. Select Arrange | Document Boundary (or type AD) to fit the boundary to the extents of the objects in your drawing and allow a further 100% scrolling space beyond them.
I hope this is helpful.