Try running Origin as Admin.
Try a Clean Boot
http://support.microsoft.com/kb/929135
If Origin and the game install location are on different partitions/HDs. Move the install directory or reinstall Origin to the same HD as the games, re-map locations as needed.
Try uninstalling Origin and Reinstalling Origin. This does not uninstall games.
Try closing any Antivirus/Firewalls. If it works, re-enable them and add exception rules for PvZ.exe
