I am using the slackbuild from SBo on Slackware64-current with multilib.
No problems with starting GoogleEarth via xterm.
Does it start via the menu? Assuming KDE --> Applications, Internet, 3D planet viewer.
When you say you have multilib installed I assume this includes the compiler and compat32 libs also?
In /lib/ you should have these links:
:/lib$ ls -l ld*
-rwxr-xr-x 1 root root 134937 Mar 24 22:01 ld-2.13.so*
lrwxrwxrwx 1 root root 10 Mar 29 06:51 ld-linux.so.2 -> ld-2.13.so*
lrwxrwxrwx 1 root root 18 Apr 28 11:07 ld-lsb.so.3 -> /lib/ld-linux.so.2*