I wouldn't reinstall Ubuntu in order to fix this problem.
Instead take unshare any folders Ubuntu One sync-daemon is attempting to sync. If this doesn't work try killing the ubuntu-one syncdaemon. Check what resources this is using in System Monitor. If the process keeps coming back and causing Nautilus to crash you can uninstall Ubuntu One with the following actions:
Go to System->Administration->System Monitor.
Switch to the Process tab, and you should find out anything that begins with "ubuntuone". Choose them, and click "End process".
Go to Applications->Accessories->Passwords and Encryption Keys.
If there is a token for Ubuntu One right-click it and choose "Delete" / Mine was actually called "default".
Go to Applications->Accessories->Terminal to open a terminal window.
Type the commands below:
rm -rf ~/.local/share/ubuntuone
rm -rf ~/.cache/ubuntuone
rm -rf ~/.config/ubuntuone
rm -rf ~/Ubuntu\ One
You should enter the following commands in terminal:
sudo apt-get purge ubuntuone-client* python-ubuntuone-storage*
Now your Nautilus problems at least should be resolved.