The web service that Google Earth 6 uses has been turned off. I can't use Google Earth 7 (incompatible GFX - it won't display satellite images, only roads).
Here's the fix:
Rename /opt/google/earth/free/libcurl.so.4 as /opt/google/earth/free/libcurl.so.4.bak (backing up original file, just in case)
Copy /usr/lib/i386-linux-gnu/libcurl.so.4.2.0 to /opt/google/earth/free/libcurl.so.4.2.0
Rename /opt/google/earth/free/libcurl.so.4.2.0 as /opt/google/earth/free/libcurl.so.4
Works on Ubuntu 12.04 Precise 32bit - libcurl.so.4.3.0 may be the newer version on your system. If you're on a 64 bit system a simple upgrade to Google Earth 7 will probably fix the Invalid HTTP Request problem