Not true. Hydrolyzed vegetable protein contains MSG (5-20%) but contains
no casein--it's vegetable protein, not animal protein.
From what I learned from one of the rabbis who answer kashrut questions
on the net through one of the kosher certifying organizations ( I think
it was the Orthodox Union, but I'm not sure), casein may be used in the
process of making the hydrolized vegetable protein.  Not knowing much
about the processing of food commercially, I took this information at
face value, and also noticed that it followed that the kosher foods I
checked in the market that contained hydrolyzed veg protein were kosher
dairy, not kosher parve.  I assumed that was the reason, but who knows?
Dale Robin Lockman