I had this same problem with my upgrade, I would click on the upgrade and it would go through the file check successful then when I click the continue button nothing.
I contacted my server company and they found nothing wrong with the server, so I moved to my Apple computer went through the upgrade process using the Safari web browser and everything worked great, the entire system upgraded, and the administration panel is great no problems, as long as I don't use MS explorer 9. This is where the problem is it is with Explorer 9 not the server everything works great with any other web browser except explorer 9 both my apple and my Dell PC but I can not use explorer 9 even now that the upgrade is done the admin panel in explorer 9 is not working.
So the problem is with Explorer 9 period and it should be looked into and fixed I know I would greatly appreciate it.