Is there a reason that VLC on OS X refuse to open Google Video files from OS X, but play all gvi's I have thrown on it by draging them to the playlist? If not, could you please add this line to Info.plist in your OS X bundle? (I used the avi icon since as far as I know gvi is just a slicesly modified avi)
<dict>
<key>CFBundleTypeExtensions</key>
<array>
<string>gvi</string>
</array>
<key>CFBundleTypeIconFile</key>
<string>avi.icns</string>
<key>CFBundleTypeName</key>
<string>Google Video File</string>
<key>CFBundleTypeRole</key>
<string>Viewer</string>
</dict>