It sounds to me as if you have wired your lights in series like this -------L1------L2------ what you need to do is wire them in parallel like this
---------I---------------------------!
L1 L2
---------!---------------------------!
Look up these key words on the internet.
Alternatively bribe any school kid of 15+ passing to explain the difference.
Test - remove one light bulb and switch on - if the other bulb doesnt then work they are in series.
Could it be all is well but you have used lower wattage bulbs?
best wishes Nyge, March 2011