Thanks for all your replies. Yes, we have considered that it may be teething problems but never did anything about it. I guess we're just enduring it and hoping it will go away, which is wishful thinking, to say the least.
We do try somewhat of a routine, which consists of various things including playing a CD with so-called sleeping songs that actually seems to work. He's asleep in a matter of minutes. I guess it's not so much getting to sleep that's the problem, rather it's more staying alseep, I think.
I also forgot about the routine where you take gradually longer and longer when tending to him after he awakes so he learns to sleep on his own. Will try that one and hope it helps. Thanks again!
David