Just follow these steps. My bro did the following after I updated BF3 with the latest patch.

1. Copy the entire BF3 game dir from Origin. If you don't know the path, check your Origin configuration.

2. Paste the new BF3 dir to replace your older version. If you want, just rename the older dir to something else as backup.

3. Repair BF3 via Control Panel/Programs and Features to fix the registry

4. Hit play