I have a few things I\'ve made in the past that have the border-radius attribute like this:
border-radius: 7px;
This is not working in IE9. I t
IE9 does support browser radius, but if you are working on a local site or local file, you should be sure the Broser Mode and Document Mode are right. To check it hit F12 and then check de values (Please see the picture). For example if Document Mode are set on Quirks Mode (which is the default) and you don't specify the document mode on the html document, IE9 may interpret this document as a IE7 document so the radius doesn't work. But if you set Document Mode to IE9 standard you will see a pretty radius on the input.
Please take a look at the picture in http://moodle.org/pluginfile.php/115/mod_forum/post/843271/IE9-F12.jpg
I hope that this can help you with the radius. :)
So long this post.