KML/KMZ files and layers can be a little complex at times and most people have issues at times. Here are some recommendations and suggestions that should come in handy:-

• KMZ files are basically ZIP files that sometimes contain multiple KML files within them. You could actually change the .kmz file extension to .zip and unzip the file then load each individual KML file as a separate layer
• The Ushahidi Map has limits on how much KML data it can load. If your KML file is a few Megabytes big, this is going to be an issue in any browser. Good sizes are in the sub-megabyte range.

• Sometimes, poorly formatted KML files will be an issue and show up blank on the map. Usually this has to do with the styling in the KML file itself. Google Earth is more forgiving. In this example, it will be assumed the LineStyle has a zero width so will show up blank

<LineStyle>

    <color>ff0000ff</color>

</LineStyle>

<LineStyle>

    <color>ff0000ff</color>

    <width>1</width>

</LineStyle>

You can find the KML reference guide here:http://code.google.com/apis/kml/documentation/kmlreference.html