When I click "Turn On Photo Stream" on in iPhoto it reports "iPhoto unable to connect to Photo Stream." It shows the correct user name on the Photo Stream screen in iPhoto. I have the correct credentials provided on the iCloud App in System Preferences, and Photo Stream is turned on there.
Running Mac OS X 10.7.2, iPhoto 9.2.1 and iOS 5.0.1. System Updates, App Store and iPhoto reports everything is up to date and running the current version.
I am connected to the Internet and able to visit iCloud.com and log into my account just fine. iTunes, and other apps all seem to work fine.