No offense but, cafeenman's right. Try other means of storing your data other than the array.

Anyway, regarding with this part...
VB Code:
  1. '------------------------------------------------------------------------------

  2.         tmpGenre = (GetID3.Genre)                 ' <--- Relevant Code

  3.     i.SubItems(5) = Matrix(tmpGenre)

  4. '------------------------------------------------------------------------------

have you checked on tmpGenre's output? Truth is, I also don't find any problems with the results.

Know first the value of tmpGenre and compare it with your Matrix if the tmpGenre's value corresponds with that of Matrix's
VB Code:
  1. '------------------------------------------------------------------------------

  2.         tmpGenre = (GetID3.Genre)                 ' <--- Relevant Code

  3.     i.SubItems(5) = Matrix(tmpGenre)

  4.     Debug.Print "tmpGenre=" & tmpGenre & _

  5.         ": Matrix=" & Matrix(tmpGenre)

  6. '------------------------------------------------------------------------------