post-slug not filtering apostropies

I’ve recently upgraded to 2.2, and have changed the permalink structure away from ?p=123 to use the post-slug. However, WP hasn’t stripped out any of the special characters, either when the post was created (should it have, in 1.5?), or when I updated the permalink structure. A lot of my posts now error out like this:

Invalid character in /2006/10/they-dona€?t-care-if-theyre-extinct/
The URL can only contain alphanumerics plus the following characters: /.,=:_-

although the url is actually:
/2006/10/they-don%e2%80%99t-care-if-theyre-extinct/

Short of going though and checking every post, is there a plugin that can check and remove everything except a-z and – from the post-slug, after they’ve all been created? Or a change I can make to the PHP with a regex that will strip out everything in a post-slug from % to one character before the next – ?

Thanks,