IE8. Replied to a post, picked the Quote link, crashed out with this:
An Unexpected Error has occurred.
Sorry, your request failed. A notification has been sent to the development team for investigation.
Exception ID: 161EED06
Please click the Back button on your browser.
Then, posing this message I got "Your post has been changed because invalid HTML was found in the message body. The invalid HTML has been removed. Please review the message and submit the message when you are satisfied."
Then, pasting the above text I got a golf ball-sized "waiting" animated circle thing pasted in as well, which I deleted.