I'm having a similar problem - but it seems to only be occurring with singe quotes.
When putting the text entry into the database I strip html tags, convert to special characters, and run it through the mysql real escape function. When the text is spit back out on the page the single quotes will either be blank (safari) or will be a question mark (firefox). Actually firefox formats the text really really weird whereas other browsers do not. But that's neither here nor there.
Any ideas about what to do with the single quote issue?