V33 Infotainment - M3GS 5-door - Genres on USB MP3

The genres displayed for songs playing on the USB ports NEVER match the actual genres on the MP3 tags. I get a wierd assortment of genres depending on which memory stick I use. Has anybody else experienced this?

What I have done so far and there is no change to the behaviour of the system

1. Tagged all songs with only ID3v2.3 tags that are ISO-8859-1 compliant. I also tried UTF-16.

2. Tried a memory stick with only 3 songs all tagged with the same genre. Got three different genres back. All songs were tagged "Rock"

3. Updated Gracenote to ver 5 (was 2).

4. Rebooted the infotainment system.

5. Tried 4 different memory sticks of varying age and speed.

6. All songs are CBR 320K or less. strict ISO. Created from Music Monkey.

7. Removed all folders. All songs are in the root directory.

TIA for any help.

Appears that Gracenote substitutes it's own genres for the ones I have (e.g. "Country" becomes "Roots". The confusing bit for me is that some of my genres remain, especially the songs tagged with multiple genres. Does anybody know how Gracenote chooses/substitutes genres? Is there a current cross-reference?