I probably shared this story before. A customer was mad that we reassigned the lead programmer (Rob) on their project to another area, and the customer wrote an angry letter to our CEO about it. The CEO handed it off to the project manager, told him to put the programmer back on the project to mollify the customer, and let the customer know.
So the project manager wrote a very nice letter apologizing about the "misunderstanding" and how important the customer was to us, blah blah blah. He closed with this:
"And I'm sure you'll be pleased to know we have decided Rob will not be assigned to your project."
That sent the customer into a rage and they called the CEO and ranted and raved about the smart-ass letter from the project manager. CEO calls the project manager and asks if he's lost his mind. The project manager was mystified at what happened.
Because what the project manager meant to write was "And I'm sure you'll be pleased to know we have decided Rob will now be assigned to your project."
... will NOW be assigned.
The kind of typo spellcheck won't catch.