Ahhhhhh! Have you tried "Compatability Mode" on the site? While viewing the website, from the toolbar, click on "Tools", and then "Compatability View". The site will refresh itself and in the URL bar, right hand side, you'll see a torn piece of paper looking icon (3rd from the end) that is now "blueish" colored...

Try and send a PM while in Compatability Mode and see if it works for you... I did and was able to send YOU a PM from IE9 which is now in my Outbox.

IE9 threw all sorts of wrenches into the mix... It was easy to walk someone through setting up our remote access solution before with IE8... "Click the link, say Run, say Yes I'm sure I want to run" and then it'd run... With IE9, you have to click the link, say yes you want to download, Microsoft doesn't realize that it's safe to run, are you sure? Yes, then you have to click more actions, then run anyways, etc, etc.... Really?

Glad I could help though. Just something you'll have with a website that hasn't been updated for IE9 standards. Little quirkiness here and there. Thankfully it was an easy fix... (Or like I said - rolling back to IE8 would've been an alternative option too).