I cannot select a single cell or pull down cell contents
 

I was in the middle of working of a spreadsheet when something changed and
now I can no longer select a single cell or pull down cell contents or
formulas. I was wondering if the scroll setting was on, but I cannot find a
way of getting back to normal so I can continue working. I shut the program
down but the problem was still there when I started up again. If anyone can
help me get back to normal I will be eternally grateful.