I don't know if anyone else has come across this but it happened to me twice today. I logged into my newly updated WordPress 3.2 site and it loaded the IE6 dashboard.
The first time it happened was in Firefox 5 and I was with a client so I just hit refresh and it disappeared.
Second time it happened on my client's computer in IE8. I took a screenshot of that one since it happened agained http://screencast.com/t/f3ld0kAXZb
I'm afraid that I couldn't investigate any further as we were in the middle of a training session. I have tried to replicate it since I got home but no luck.
Here are the plugins I have installed:
Admin Footer Text
Contact Form 7
Simple Google Sitemap XML
WPMU DEV Update Notifications
Let me know if you need any more info.