I also had the exact same issue after upgrading to 1511. Fix was to download the driver rar package, and reinstall the driver as mentioned above.
However I also faced intermittent WiFi issues.
Looking at this page here, http://techtablets.com/forum/topic/broadcom-wifi-driver/
I noticed my driver version was 1.248.1.0 (or similar), I’ve updated to 1.48.0.0 and it seems fine thus far.
