There's a new installer available if you go to http://earth.google.com/download-earth.html
(It's not yet available via Check-for-updates, but that should change early this week)

It is v4.0.1657 (Windows), v4.0.1658 (Mac), and v4.0.1660 (Linux).


It has the following fixes:

Changes From Version 4.0.1565
-----------------------------

- Language selection in client: Tools->Options then the "General" tab

- Restore missing Search/Places/Layers panes if the user chose to hide them in version 3.0

- Scroll wheel now defaults to "zoom in" for "wheel up". The setting can be
reversed in Tools->Options then the "Navigation" tab

- More reliable reading and writing of kmz files on systems with non-ascii
usernames

- Fixed imported terrain for SketchUp occasionally showing 'divots'

- Client now remembers the checked status of all layers between restarts

- Improved memory management, client does not require as much memory

- Automatic setting of memory cache based on machine RAM, improves
performance and prevents flickering overlays

- Fixed warnings about Software Emulation and DirectX on Mac and PC systems

Developer Notes:

- Fixed <Update> tag operation

- Fixed deletion of local kmz file when linked to by network link

- Fixed style information being lost upon restart of client (for some styles
that were shared across a folder)

- Using <Update> on LineString coordinates now replaces all coordinates
rather than appends

- Fixed network link occasionally going into fast continuous refresh