<VV> No low beams...

[Cash Case]

Hey guys-
This is odd. I replaced the driver's side low beam headlight because  
it wasn't working.
I buy a new bulb and turn the headlights on. No low beams. Then I try  
the high beams. All four lights go on. I the old bulb is good. I  
should've turned the high beams on.

Anyway, what would make the low beams on the drivers side not work  
unless the high beams are on.

-Cash