Because your skinmesh has too many bones. More than 21 bones crashes the toolset (and more than 24 crashes the game).
Here's what CM352d makes of your model:
c_talbukbl.mdl loaded.
skinmesh talbukblue re-aligned to origin
skinmesh talbukblue re-pivoted to origin
*** Error *** more than 21 bones in talbukblue
vertices welded in [talbukblue]
duplicate face(s) deleted from talbukblue
unused tverts deleted from [talbukblue]
tverts welded in [talbukblue]
Fixes made = 19274
*** Cannot output model - too buggy ***
Try cutting the skin into separate pieces, so that each piece has <21 of the bones.