See the attached screen grab! I'm using IE9 on Windows 7 SP1 with every update under the sun installed, seems to work fine in Firefox and Chrome on the same PC.
Ahh, you're using TinyMCE. That'll be where the bug is, not Beehive. I have upgraded to the latest release, consider this post a test to see if it fixes it.
Had to clear my internet cache as well, just in case anyone else is suffering from the same thing. Thanks for the fix Matt.
Have you considered using YUI Editor? It's on the Yahoo! and Google Javascript CDN servers, might help bandwidth etc.
First time I've heard of YUI Editor (I've used the YUICompressor). I shall have a look at it sometime.