iPhoto unable to connect to Photo Stream

I've searched on Google and tried a few different things but have had no luck so far, so I'm hoping someone on here can help.

I'm on Lion and running iPhoto 11 (9.3). I have iCloud and Photo Stream running properly on an iPhone and two iPads, but can't get it to connect on my Mac at home.

I've checked the check box in the iCloud preferences. I've tried signing out of iCloud and then back in. I've tried to go through the steps at http://helpdeskgeek.com/help-desk/photostream-keeps-turning-off-in-iphoto-fix-it/ but don't seem to have the folder iLifeAssetManagement on my machine. I also don't have the plist files listed as Method 2 in the link above.

Any ideas anyone else can recommend?

Thanks for your help.

Yes. The message "iPhoto was unable to connect to Photo Stream" comes up when trying to enable it.

Also, don't have Aperture so that wouldn't be interfering with anything.

Upgraded to iPhoto 9.3.1 last night. Still have the same issue. Just bumping this up one time to see if any other help can be offered.......