Same problem here, but now fixed.
- iPhone 4S, iOS 5
- iMac
- iPad 1
- AppleTV
- Airport Express
iPhone is the only device that takes pictures; had not been syncing them to Photostream since Nov 4th (just noticed today, Nov. 18th). I have my iPhone on Wifi often, in various places, and normally the photos update fine, so I do not think restarting my home Wifi (Airport Express) is the reason.
I did the following things, listed in order, and new photos are once again uploading to Photostream, though all photos from Nov 3 till Today are not uploading.
- Killed all Apps on the iPhone (had over 40 Apps open)
- Restarted phone (hold both buttons for full recycle)
- Took a picture - photos NOT syncing
- Turned Photostream ON/OFF on the iPhone
- Took a picture - photos NOT syncing
- Turned on Airport mode ON, then turned Wifi ON; Chose my normal home network (Airport Express)
- Turned Photostream ON/OFF on the iPhone
- Turned Photostreaming OFF on AppleTV
- Took a picture - Photos started syncing at this point
- Turned Photostreaing ON on AppleTV
- Took a picture - photos still syncing
- Turned Airport mode OFF
- Took a picture - photos still syncing
Not sure exactly where the issue was, but possibly had something to do with Airport mode/Photostream ON/OFF/AppleTV comboination starting at step 6? (makes no sense to me). Hope this helps.