NVIDIA pushed out the Software Update v1.1 for the SHIELD tablet K1 and v4.0 for the original SHIELD tablet, but the update was pulled a day later. Apparently those receiving the update often lost WiFi functionality, which is pretty crappy on a WiFi-only tablet. Thankfully, it seems NVIDIA has fixed the issue.
The two updates are both rolling out again to their respective devices, and NVIDIA is confident the issue has been resolved. Check for updates in the settings app to pull it now! Or wait a few days, let someone else test it for you first. Who knows, you might avoid more issues.