Issues with Special Characters

Hello, Wondering if anyone can help me with a strange issue (or offer advice). I have an instance of WordPress running on a client site and all of a sudden it won’t save special characters (‘ ” ™ ? etc.), even when I use the tinyMCE Special Character pop-up chart to add them to my content. In fact it cuts off the special character and everything else after that on the page when I save the page.

I’ve made sure to paste from notepad, because I have seen other sites when the characters turn to ?, but never seen it cut it off and everything else after, even when using the tinymce special character pop-up to add them.

Seems to have started to happen all of a sudden.

Thanks for any help.