You don't say if you've measured/adjusted it, but It's possible the truss rod has too much tension on it.
Most guys seem to fall into two camps with those - they either regard it as a black art and leave it to somebody else to mess with, or the just adjust the hell out of it until the neck is so out of whack it would make a better Hot Wheels track than a neck.
Wheeee! Check out my neck setup!
But, it's really not that tough to do well, given the proper tools. They'll cost you a few bucks, but they'll pay you back handsomely if you own or plan to own more than one guitar. One caveat: you'll be able to do something well that most guys can't, and suddenly everyone will want to be your friend <grin>
But, all you really need is a
good straightedge and some automotive-type feeler gauges.
Feeler gauges are quite inexpensive - it would be weird if you had to spend more than $8 or so for a full-tilt boogie set like this...
They range in size from 0.0015 to 0.035" (0.038 to 0.889mm).
Good straightedges are a different story, though.
The one I use (and I tried
really hard to find something similar at a better price) comes from Stewart-MacDonald.
You want something at least that good, and you want the 18" version. They're $47 from StewMac; I don't know what that translates to in pounds or euros.
Anyway, you lay that across the frets to see where the 'board is high/low, and if it's gradual, you can often take that out with about a 1/4 turn of the truss rod adjustment. High in middle, you turn the adjuster counter-clockwise (loosen it), and vice-versa. Use the feeler gauges to find when the 'board is level - you shouldn't be able to get a .001 feeler under the straightedge on any fret.
If you've lived well and brushed your teeth regularly, then once you're there you want to put some relief in the neck. That's accomplished by loosening the adjuster. It never takes more than a 1/4 turn to get where you want to be, so small movements are in order. Depending on how good a fret job has been done, you'll want somewhere between .008" and .012" of relief at the 8th fret. Smaller is better, but there's a limit. You have to leave room for the string to vibrate, or you'll get dead spots and buzzes. Once you're there, string it up and call it a love story.
If you've been a bad boy, relaxing the truss rod won't take the bow out, and you get to go get drunk and smash something up. Fixing that is not a trivial task.
While we're on the subject, another tool you might want to invest in as long as you're paying for shipping from the other side of the world is a "
fret rocker".
Invaluable tool. For the $20 one costs, you'll wonder how you ever lived without it. I resisted buying one for a long time, making do with other tools because this one looked like a bit of nothing at the price. But, trust me - you want it. Of course, if you don't buy the files to take care of the problems it exposes, all it'll do it piss you off by pointing out problems you can't do anything about. But, at least you'll know what the problem is so when you take to someone who's invested in the files/polishers/etc., you can tell them what's up.