Found the answer:Re: Mountain Lion Notes Crash When Using MS Exchange Notes
I was having the same issue! I finally found a solution to it!
1. Delete your exchange account from the Mail, Contacts & Calendars pane in System Preferences.
2. Go to Finder, click "Go" in the menu bar, click "Go to Folder" and type in "~/Library" (without the quotes) in the box. This will take you to your user Library folder.
3. Use the search box in the finder and type in "com.apple.notes" and click "Library" in the search bar that appears. This should now find several folders and files related to the Notes app. Rename or delete everything except the help files (with the lifesaver icons on them). Just to be safe, I'll list the files and folders you should delete or rename and their directory paths:
com.apple.Notes - /Users/danieloria/Library/Containers/com.apple.Notes/
com.apple.Notes - /Users/danieloria/Library/Containers
com.apple.Notes.plist - /Users/danieloria/Library/Containers/com.apple.Notes/Data/Library/Preferences
com.apple.Notes.savedState - /Users/danieloria/Library/Containers/com.apple.Notes/Data/Library/Saved
4. Restart your Mac. Put your exchange account back into System Preferences, you can go ahead and activate the Notes sync service.
5. Open Notes and it should be working now!
NOTE: I also deleted all the stored information related to the exchange account in Keychain Access when I deleted the 4 com.apple files. This may or may not be necessary, but I just thought it was worth mentioning.