File Consistency Error for Gun Skins

I DL'd a bunch of new gun skins for 1.6 and in every server i go into (even just when i do "new game" and pick a map) i get this error:

Server is enforcing file consistency for models/p_ak47.mdl
Bad file Server is enforcing file consistency for models/p_ak47.m

but its not just for that model, its for ANY custom model i put in.

now i know u might say "then just delete the model and get a new one, or play with the normal skins", but i hate the defaults -.- and the thing is: ive used the skins in servers before! the exact same ones (i had to Re-DL cuz my HD crashed). and now all of a sudden they dont work anymore.

any ideas as to why this may be happening?