I’m not sure that is correct, certainly in my situation.
I have many wordpress installations on my server, and have only upgraded one to 3.5 and it’s the only one with problems.
I have just updated the plugins on a different site, just fine. I even checked the permissions on the wp-content folder and it’s children. All fine. And more importantly, all the same on the both sites. One works, and one doesn’t.
It’s odd that the upload a zip file works, but the updating and installing from the web doesn’t.
My money is on the streaming component and maybe a compatibility issue with a version of PHP?