Yasper -
If the truss rod has never been adjusted then it is possible some of the glue to bond a fretboard or skunk stripe has adhered to the rod. Generally loosening the rod to break the jam free works.
Setting the truss rod on a bass or guitar should be done in very small, 1/4 turn incremental stages. Give the neck a few days to settle in to the adjustment before you adjust it again.
Some other things to consider is the angle of the neck to the body. The head may be back too far causing the buzzing.
Have you adjusted the saddle height to remove the fret buzz?
What condition is the nut in?
One other thing, if you've recently changed string gauges? That can cause the neck to respond differently.
Here's a link to give you a little information on
truss rod adjustments.
If you have a good shop in the area with someone who can do a professional set-up then it's not a bad idea if you don't feel comfortable making the adjustments yourself.
Happy Trails
Cynical One