After an update from 4.x to googleearth-5.0.11337.1968-0medibuntu10, my placemarks are displayed at the wrong positions. If I double-click on the placemark in the "My Places" tab, Google Earth jumps at the right position of the placemark, but the yellow pin is shown at a different point whose coordinates are only the degree part of the coordinates of the placemark -- the minute and second part of the placemark's coordinate are ignored. This wrong coordinate is also displayed in the "Properties" dialogue of the placemark.
I found out that Google Earth writes bogus coordinates to myplaces.kml (it uses commas instead of points for decimal separators) when the locale is set to de_DE.UTF8, which is the case for me.
I found a workaround on the Google Earth issue tracker [1], which suggests to use LC_NUMERIC=en_US.UTF8. Maybe the startup script or the application starter could be changed accordingly.
[1] http://code.google.com/p/earth-issues/issues/detail?id=330&q=locale&colspec=ID%20Type%20Summary%20Status%20Owner%20Stars
I can confirm this bug. In my case all gpx files I try to import have bogus coordinates.
My default locale (LC_NUMERIC) setting is nl_NL.UTF-8
When I manually set this in a terminal to 'en_US.UTF-8' and use that to start googleearth it works good.