first, make sure that when you apply power, the top line of the LCD displays solid blocks. If this is the case, try the additions i suggested above.

If this is not the case, you probably need to have a contrast control for the LCD. You need a variable resistor and hook it up like this:

Code:
LCD pin 3
   |
   |   +5v
   |    |
   |    |
   |    \
   |    /
   ---->\ variable resistor (10k or bigger)
        /
        \
        |
        |
       gnd