It seems to be a problem related to a missing, or incomplete, GarminDevice.xml.
Try to open it with a text editor, or with the browser itself.
If you can open it (you find it in the folder \Garmin) you should find the following types of sections

- <DataType>
<Name>BaseMaps</Name>
- <File>
- <Specification>
<Identifier>IMG</Identifier>
</Specification>
- <Location>
<Path>.System</Path>
<BaseName>gmapbmap</BaseName>
<FileExtension>img</FileExtension>
</Location>
<TransferDirection>InputOutput</TransferDirection>
</File>
</DataType>
- <DataType>
<Name>PreProgrammedMaps</Name>
- <File>
- <Specification>
<Identifier>IMG</Identifier>
</Specification>
- <Location>
<Path>.System</Path>
<BaseName>gmapprom</BaseName>
<FileExtension>img</FileExtension>
</Location>
<TransferDirection>InputOutput</TransferDirection>
</File>
</DataType>
- <DataType>
<Name>SupplementalMaps</Name>
- <File>
- <Specification>
<Identifier>IMG</Identifier>
</Specification>
- <Location>
<Path>Map</Path>
<BaseName>gmapsupp</BaseName>
<FileExtension>img</FileExtension>
</Location>
<TransferDirection>InputOutput</TransferDirection>
</File>
</DataType>