Why this arrow key 'scrolling' behaviour?

[Terry Pinnell]

With a cell selected and I press an arrow key, what should happen? I'm
99% sure that the selection used to move appropriately to the adjacent
cell (right/left/up/down). But now the whole worksheet is moving, i.e.
scrolling (right/left/up/down). Is there some setting I've
inadvertently changed please?

 

[Terry Pinnell]

With a cell selected and I press an arrow key, what should happen? I'm
99% sure that the selection used to move appropriately to the adjacent
cell (right/left/up/down). But now the whole worksheet is moving, i.e.
scrolling (right/left/up/down). Is there some setting I've
inadvertently changed please?

[Minutes later]
Duh - I had somehow pressed the Scroll key!