This worked for me. Thanks Justin.
1. click on mac HD/ libraray /caches. drag all the contents in the folder to the trash
2. click on the finder click go, hold the option key and clikc on libraries (will not appear if you don't hold the option key). go to the caches folder again and again drag everything in the folder to the trash.
3. click on the finder click go, hold the option key and clikc on containers. Drag com.apple.notes to the trash
4. restart your computer.
5. empty trash.
6. try to open notes again
Worked for me as well, had two ~/Library/Containers/com.apple.Notes/Data/Library/Notes/ folders and deleted one (Notes) to rid my self of the two icloud account problem. Rechecked iCloud account and all notes returned. Make sure to move all notes to active iCloud account and check sync before doing this.
Process: Notes 
Version: 1.5 (107)
Build Info: Notes-107000000000000~3
Code Type: X86-64 (Native)
Parent Process: launchd 
User ID: 501
Date/Time: 2013-07-19 12:33:39.235 -0500
OS Version: Mac OS X 10.8.4 (12E55)
Report Version: 10
Interval Since Last Report: 359983 sec
Crashes Since Last Report: 9
Per-App Interval Since Last Report: 7 sec
Per-App Crashes Since Last Report: 9
Anonymous UUID: AE416A17-5C9A-DC6E-5228-DBA27EB4130D
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Application Specific Information:
*** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<SharingController 0x7f9cf3a360e0> addObserver:<NSKeyValueObservance 0x7f9cf3c09970> forKeyPath:@"delegate.sharedNote" options:256 context:0x0] was sent to an object that is not KVC-compliant for the "delegate" property.'
terminate called throwing an exception
Tried every solution I read in all support treads ... NOTHING WORKS!?!?! ANYONE?!?!
I did all this, and then realized (too late) that I was not backed-up by Icloud. Now -- Notes does open up (was continuously crashing), but all notes content is gone. I did not empty trash with com.apple.notes and other files/ folder and now have on my desktop, but can't seem to place it back correctly to bring back Notes content when relaunching.
There are several of these com.apple.notes folders I see in various places in Container-- so perhaps I am not deleting newer ones, and putting old one back correctly -- and I can see the folders there currently do not have much in them (KB), indicating that they are not the original Notes data (I had over 200 some notes). Folders I do have saved to put back is com.apple.Notes folder with file cache.db-wal which is 3.1MB in size. Also Notes folder with a file NotesV1.storedata-wal which is 4.1MB size.
Any advise on how/where to replace com.apple.notes and Notes folder mentioned above -- to restore original Notes data. Before I emptied out the cache's and container folder -- I was at least able to find the individual Notes documents via Spotlight search -- but now Notes program has not content, and nothing shows on Spotlight search.
I hope the notes content is not lost forever. Can you help?
I've had this happen to me twice in Mavericks. Once back in Decembr 2013 and then again today. Each time, the culprit was a Login item that was not playing nicely with the rest of the system. I simply deleted it and everything was fine.
To do this, go into System Preferences --> Users & Groups and click the Login Items tab to see a list of applications that open automatically at login. At this point, you can either delete all the ones that are not from Apple and then restart, which should fix the problem. Or you can try deleting one at a time (restarting each time) to see which one is the culprit.
I noticed the same issue the first time I opened Notes after upgrading to Yosemite. I have two accounts with notes synced, i.e. Gmail and a corporate Exchange one. I suspected the problem came from the Exchange one, but I wasn't sure.
The following worked for me:
1) disabled the Notes syncing for both accounts in the Accounts settings in System Preferences
2) moved ~/Library/Containers/com.apple.Notes to Desktop (could be moved to trash of course) as suggested above
3) did a Logoff
4) opened Notes to check: now it worked fine, but of course my notes were gone.
5) closed Notes
6) re-checked Notes syncing for Gmail in System Preferences: it worked fine after a couple of seconds 'spinning'
7) try to re-check the Notes also for Exchange, but after a much longer 'spinning' the option was again unchecked. So I deleted the Exchange account entirely and re-created it with Notes checked: now it worked fine
8) opened Notes again, and now all the notes from both accounts were back and the edit/sync worked fine.
I think the point is that for some reason the data present in com.apple.Notes did not survive the upgrade to Yosemite: the cleanest way to recover it is to force the system to rebuild them by syncing with the servers from scratch.
Hope this helps