NOTE: These instructions are obsolete. The fix has entered the default repositories. If you are still experiencing freezing, your problem is different from the OP's. Please open a new question about it (after reading What should I do when Ubuntu freezes, of course).

Known bug.

Solution:

1. Open Update Manager


2. Click the Settings button


3. Check the box Pre-released updates


4. Click the Check button in Update Manager


5. Install the updates


6. Reboot

Problem solved.

Optional:

• Uncheck Pre-released updates in Update Manager settings to avoid getting potentially unstable updates in the future