Certain genres are in the ID3 system are given numeric values and media players can display a value localized for the current region. My guess is that there may be some corruption of the localization file. These files are found at:
C:\Program Files[ (x86]\iTunes\iTunes.Resources\<Two letter country code>.lproj\localizable.strings
Try deleting the active file that corresponds with the region you have selected in iTunes settings, then run a repair on iTunes.
Here is a list: http://en.wikipedia.org/wiki/ID3#List_of_genres
BTW, which region is iTunes set to? Do the numbers match your expectations?
tt2