From what I gather, their belief is that Christ was created, and not always. I think they have a good point, and I'm not even sure if it goes against the trinitarian belief.
Hope someone sheds a bit of light on this one.
Yes it does contradict trinitarian belief, because Arians believe Christ was created by God the Father. That is, God the Father is superior to the son.
To some christians this means that "a fundamental issue involving the integrity of the Gospel was at stake: whether God was really in Christ reconciling the world to himself."
But I wouldn't know about that.
Jehovah's Witnesses are in effect Arian, you can see here that they do not believe in the Trinity. [www.beliefnet.com
"Belief in Deity
There is one God Almighty--a Spirit Being with a body but not a human body. There is one God and no Trinity.
Christ is Lord and Savior, but not God (Jehovah) incarnate, not a God-man but inferior to God, not part of a Godhead. He was a created spirit being, God's only begotten son, sent to Earth as a perfect human."
Hope this helps :)