At the time I was working on a machine with Firefox 5.0.1 (I don’t have permissions to upgrade). I’ve gone ahead and tried it on Internet Explorer and it works fine, so it might be a version issue.
I have managed to get into the file structure and have disabled ALL of my plugins. I did update multiple plugins yesterday, but I’d done them one at a time and didn’t see an issue until after the Jetpack update. However, I will be investigating each one to see where the error or conflict arose. Turning on Jetpack by itself seems to have created no problems, so …