Neutered Male mounting spayed female

Question
I saw this question was previously addressed but, my situation is a little different.  I recently acquired(6/25/09) a  
yellow lab, 2 yr old n.male, he was neutered almost a year ago.  We already have a spayed 4 yr old yellow lab
female. The male has next to no training so he is crated in the house and has play times, training times and
bathroom breaks all his time is supervised and the training is going well I am using a reward method.  The
playtimes are pretty good in the beginning but after my female gets a little tired and he is still full of energy, he
continually tries to mount her and gets that look about him quite frequently.  He gets fully erect and will even try
to hump her head.  It is so frustrating to see.  She then seems to encourage him by smelling his butt which in-turn
gets him excited again.  She doesn't seem to want to be mounted but, is too tired to fight him off.  I know it's new
and exciting for them but this is one reason I would never deliberately get a male dog.  What can I do to
discourage him from mounting or trying to mount her?
Thank you so much, in advance for your time and attention to this.

Answer
I suspect that if your female really didn't want him to do it, she might be more forceful in her objections, but either way your male dog should respect your wish to have him stop any behavior, not just that one.  Dogs that are trained to "leave it" and "come" can be asked to perform those alternatives to whatever behavior they are already engaged in.  So, I suggest you learn to train those two commands first. Get a good positive trainer to help you, or start with the free lessons at www.clickerlessons.com.  There's a good DVD available at www.cleanrun.com called "Really Reliable Recall" (Leslie Nelson).  That will help you train a top notch "Come!" on both dogs, which is worth doing regardless:-)
Humping is not always about sexual issues, but it can be - even neutered males think it's fun sometimes.  Other dogs do it as an expression of status.