What does Calibre say in the lower part of the program?
If its not 0.8.8 go download and install it.
PS, chrome is my browser of choice at present.

edit - your not expecting it to auto install are you? = clicking on upgrade when the popup from calibre appears, just directs you to the website to download the file, not show you what version you have.
Just download
http://status.calibre-ebook.com/dist/win32
then just install, over the old one is fine as I understand