You always hear that classic line "it's not you, it's me" when it comes to trying to break off a relationship. I think the statement is meant to make the other party feel better, and it's also a way to end any discussion. If it's me, then there is nothing you can do to make things better.
LinkedIn recently used this familiar refrain to populate its error page. Instead of the boring and standard "the page you are seeking is not available", LinkedIn added some humor. "Oops! It's not you. It's us. Give it another try, please." Their message made me smile instead of scowl even though the page I was seeking was indeed not available.
Think of how you can add a twist on your messages to a) take ownership of the problem and b) to make your client just a bit less frustrated that it is not there. That's not for me to do, it's on you.