Well I posted a topic about this about a month or so ago. I can assure you it happens to alot of guys, me included.
I still have this problem and haven't quite gotten around it yet, even with the help of Cialis or Viagra.
It seems better with ladies I am familar with and comfortable around, but it does seem like the first time I am with a lady, forget it, we aren't going to get it up and it's just the way it goes.
I have now taken to talking with the ladies before hand and politely tell them to be aware of it, because I don't want any suprises during the first play date. All the ladies we have been with have been extremely understanding and patient, which is helpful. You just learn to please them in many other ways and I am still waiting for the evening when all goes fine for me.
Be patient and honest with your playmates and eventually it will work it's way out. I know Mrs Van and I have discussed this and we think a large part of my issues are the fact that even though she says it is ok, I still feel like I might hurt her if I have too good of at time. I know she won't be upset, but convincing my mind of that is a different story right now.
-Van