No sorry, never heard of it before...

Any idea why this happened in the first place?

You can rename them directly in the tree and everything will be updated correctly. A bit tedious if there are many but it will work the best.

I dont know what I did (reinstalled MM, iPod update or something else) that screwed my genre list...

Now my genres are like this:

A
Am
Amb
Ambi
Ambie
Ambien
Ambient
A
Al
Alt
Alte
...
Alternate Rock
.....

Is there anyway I can rectify this? Can I delete particular genres (my songs have multiple genres)

Pl help