Looks like the key is
1. Turn off Photostream
2. Delete the ILifeAssetManagement Folder
3. Secure Empty the trash to get rid of the folder
4. Delete all photos in photostream from a device that can actually reach photostream.
5. Turn on Photostream from within Aperture
You said, you created a new library? Which library are you using now?
Make sure, your library is o.k.: Aperture 3 User Manual: Repairing and Rebuilding Your Aperture Library
Have you checked with iPhoto, if the Photo Stream works?
If the Photo Stream does not work with iPhoto either, the Photo Stream may contain a corrupted image. Try, if deleting the Photo Stream Cache will help, if you have not already done so. The contents of the Photo Stream is stored in your User Library:
If you want to save the contents of the stream, copy it to a backup location, before deleting from the library.
To reveal your hidden user library in the Finder, use the Finder's "GO" menu: Bring the Finder forward and use "Go > Go to folder", then hold down the "Options" key ⌥, until the library appears in the drop down menu.
More general Photo Stream advice is here:
Some Photo Stream issues can be fixed by logging out of your iCloud account and logging back in, then turning on Photo Stream from within Aperture (not in System Preferences). Give this a try and see if it helps any:
1. Quit Aperture if it's currently running.
2. Open System Preferences and select iCloud. Turn off Photo Stream, then click Sign Out.
3. Log back in to your iCloud account but do not enable Photo Stream.
4. Launch Aperture and bring up Aperture > Preferences. Select the Photo Stream tab and enable My Photo Stream to turn on Photo Stream. (This will automatically turn it on in System Preferences too)
WIth luck Photo Stream will run normally and return Aperture to a snappy state.
I'm using the new library, and I've followed the steps to repair and rebuild my library. The photostream does not work with iPhoto either (just checked). I've also logged into icloud.com and deleted my entire photostream. That did not help either. Deleting the photostream cache also did not help.
Thanks for the suggestions,
I am having the same problem and pretty much have tried everything suggested in this post as well as what you have tried originally. I also have Photo Stream on a PC. The problem seemed to start out of the blue which is not helping with the troubleshooting. I have disabled all third party apps with aperture like Flikr and Facebook. As soon as I turn on Photo Stream either in System Prefs or just in Aperture, Aperture hangs. I have deleted the Plist to Aperture and iLife. I have also deleted all plist and reinstalled Aperture which did not help. It appears it might be a problem with the library itself but I am not sure how to proceed from here. Will let you know if I find a solution elsewhere but there is not much out there on this topic.
I may have stumbled upon the solution. I thought I had tried this before with no success but it may have been a file and not the folder. Try shutting down PhotoStream. Go to Library folder and delete ILifeAssetManagement under Application Support ~\Library\application support\. Reboot and then restart Iphoto from within Aperture. Mine hung for a second and then resumed normally. It should be noted that I had deleted all photos from PhotoStream previously. Hope that helps and that it holds.
Brilliant! This solved my issue. All I did was rename the ILifeAssetManagement Folder and a restart for good measure. On re-enabling photostream, the ILifeAssetManagement folder was recreated and is over 10x the size of the backed up version but that's because it's working and downloading my photos (which I didn't touch btw). Original backup folder was only 10MB.