It sounds like your WLM accounts and folders are ok.
It's just the "All sent items" Quick view that isn't working.
With Windows Live Essentials 2012 you can do a Repair from Control Panel > Programs and features.
I'm not sure if Windows Live Essentials 2011 has the Repair option, but you can check.
If you do a Repair or Uninstall/Re-install I suggest backing up all data first.
You could also try updating to Windows Live Essentials 2012.
Here's a link with a screen print that shows the Repair option: How to remove and reinstall Windows Live Essentials