ok, i own bitches so i dont have this problem myself, well kindof!!
one of the boys i have bred has had a few offers of being used at stud, i am very good friends with his owner so want to help as much as i can,, yes before you ask he's tested to the eyeballs for everything, and is superb at his job, hence him being approached so much.  
his first experience however wasnt good, the bitch simply wasnt ready, as we suspected, and we had to abandon the mating, she told him off several times, each time was getting worse, and we couldnt risk damage to him.  he had another liason a year later,  another bitch, but a maiden like him,  she threw herself at him, couldnt be more co-operative if she tried!! but she squeaked when he tried mounting her and he just laid on the floor as if apologizing to her!!!! he didnt try again after that, did everything else but not actual mating!
has the 1st bitch put him off mating do you think? ive never come across this, but like i say i have the easy going girlies!!;-)

his owner is worried as she has another bitch wanting to use him this weekend, she is worried now he wont be able to perform....or that she has to think of the possibility hes gay!! sorry couldnt resist!  i cant be with her for moral support this time as im away, so any advice would be great!

It is quite possible the second bitch wasn't quite ready either.

It is usually best not to try mating two maidens for the reasons you have stated.

An experienced dog would not have worried about the squeak if the bitch was otherwise ready and willing.

It is a good idea for a maiden dog to meet his intended several times from just before they a re ready so they know they will be told off to when they are rampant.  In this way a male learns how to behave with a bitch at various points in the cycle, when to be patient and when to be more forceful.

I have handled a few males at stud and to be honest prefer to first introduce dog and bitch about two days before she is likely to be ready.  Teaching a male stud work requires some Patience and some luck and co-operative good natured bitches.

thanks brainless, he is going to a bitch who has mated quite easily before at the weekend, he's met her a few times too, so fingers crossed it will happen!

just an update from my question ( i noticed a lot get left by the by!!)

he had a slip mating the 1st day he met her, then 2 proper matings and ties! no messing about, the 1st time they played a little first,
it really did make a big difference using him on an experienced bitch! 

Good luck that should stand him in good stead for any future stud work even if he doesn't get the chance for years.

aww thats good, best of luck to the owners with the pups etc.