I realise I'm a little late to the party here but he did deliver the message correctly as far as he was aware. He must misunderstood one part of it.
Tristan will have said this to him:
"Tell her that I'm going to find Victoria and tell her that I'm sorry but I've found my true love and I want to spend the rest of my life with her"
However the innkeeper didn't realise that the 2nd instance of 'tell her' was part of the message and not an instruction to him to give to Yvaine.
So instead of the message "He's gone to find Victoria and tell her that he's sorry but he's found his true love and wants to spend the rest of his life with her" being given to Yvaine, instead she got "He's gone to find Victoria and he's sorry but he's found his true love and wants to spend the rest of his life with her"

He didn't lie, he just delivered it out of context because a) he was drunk and half asleep b) he didn't really give a beep
You just killed my girlfriend..thats actually.kinda pissing me off.huh.

It's a matter of grammar. He gets the message right but the inflection wrong. He doesn't lie, he just repeats it in correctly, it's not far off word for word to what Tristan says.
You never know when you might need a pink flamingo in your pocket!

It was a plot device to make Yvaine heartbroken. You shouldn't go looking for meaning or consistency when it comes to entertainment.

He messed up the message because he was half asleep from smoking when he was given it.

This scene is removed from the dvd I rented. I saw this movie two years ago, and I knew he spoke to him. I don't understand why that scene was taken out. This seems to be a patten, the dvd that says rental on them, are not giving the full picture. It's like if you want it all, you have to buy it.

Saw this for the first time over the easter weekend..Tristan wanted to write a note,and couldn't get either pen or paper from the Guy downstairs,so asked him to pass on the message..and the guy bollixed the telling of the message..
If Book was in Intelligence B4 finding God,does that mean He's a Shepherd Spy? (Thank You,Spike..)

He got the message wrong because he was drinking. Tristan was going to tell Victoria that he was sorry that he had found his true love, and was going to spend the rest of his life with her.