Hi.
Steps to repair myplaces.kml have been posted here:
http://www.google.com/support/forum/p/earth/thread?tid=3994c32401243da1&hl=en
If have bunch of non-printable characters in the KML file then you
might try commenting out large sections until at least it becomes a
well-formed XML file. See that discussion for details.
<Folder>
<Placemark>
...
</Placemark>
<!--
start of bad character block
...
end of bad character block
-->
etc.
</Folder>
It's tedious but not impossible!