It is strange, when I tried to upgrade some of my blogs to WordPress 3.1.2 I see following error:
Downloading update from http://wordpress.org/wordpress-3.1.2.zip…
After sometime it remains same and doesn’t show any error.
Today I was trying to upgrade MacBook Pro website and encountered this error.
It happened with plugin upgrades as well.
Since I haven’t changed any server settings and I had done successful upgrade to my other blogs on same server I couldn’t see any problems with server as such. The problem might be with WordPress website itself?
I tried it again from another faster Internet connection and it worked. It was slow in upgrading but finally it upgraded without any problem.
So if you face similar problem, either try it later when Internet is faster.
The other solution which worked is to click updates link in left column again while you are stuck and then upgrade.
If you manage to upgrade successfully in this process then dont’ forget to reinstall just in case something is missed.