The key is the slant of the apostrophe.

When I copy paste from Word or some other word processing document into the message window, I have noticed that my apostrophes (') become slanted towards the preceding letter as opposed to being straight like the example in parenthesis above.

For some reason when the apostrophe gets slanted that way, the message board converts it into a question mark (?).

Straight (')

Slanted (?)

I don't know if it is a font thing or a message board thing but it isn't the only time I've seen the problem. One thing you can do is; after pasting your message, type over all of your apostrophes in the message window so they are straight and the question marks will disappear.

I use the spell check on the Google Toolbar which makes life a lot easier.