Status (by robm at Tue Feb 17 00:46 UTC)
For the last 12-24 hours, users using the old interface with Internet Explorer would have been experiencing random problems when clicking buttons in the web interface.
Unfortunately this problem occured because there’s a bug in Internet Explorer when using certain HTML constructs. The new interface works around these bugs, and stores a flag saying "this bug can be worked around" in the users session information. With the rollout of the new interface, that flag was being set in the users session, but when they were then directed to the old interface, the code there didn’t work around the bug, causing the problem to appear.
Some new code has been added to ensure the old interface doesn’t generate the HTML construct that causes the bug.