I've now confirmed on two different machines that with IE10 the enter key no longer works when editing / making posts. It's a known problem and documented at http://www.vbulletin.com/forum/foru...problems-and-troubleshooting/420279-enter-key You need to change IE to compatibility view mode to re-enable it, the broken page icon in the top right. This can also be done with an extra tag in the page http://evolpin.wordpress.com/2011/02/25/ie9-compatibility-and-the-meta-tag/
Thanks for figuring that out. It was rather frustrating having to open a different browser all the time if I wanted to post.