My dock is...messed up

My mac is less than 2 months old, and its the 13" standard model (Core i5) the dock will open applications and everything works as it should. Except for the lines that allow me to shrink and expand it. I mouse over it and instead of getting the line with the arrows, it stays as the normal mouse. and if i click and drag it nothing happens. EVERYTHING else works fine ( dock related).