Google has just pushed out version 126.96.36.1997, replacing version 188.8.131.529 for most people. The “check for updates” feature doesn’t seem to be finding it yet, but if you download Earth from their servers (earth.google.com), you’ll get the new version.
As far as I can tell, there aren’t any official release notes available yet. However, you can find a few tidbits about the release in this thread in the KML Developer Support group.
Based on that information, it seems that this release fixes a variety of bugs in regards to 3D/polygon handling. Grab the update here and if you notice any other changes, please leave a comment and let us know!