Tokina 11-16, error 01, clean contacts

[claude]

I recently purchased the 11-16...took about a 15-20 great shots outdoors...during tht time received the error message 2-3 times...removed lense and re-attached several times....yesterday got the error message about every two-three shots...now it barely works. None of any of my other lenses produce a single error message. I'm using a Canon 50D. I am hoping the store I purchased it from allows me to return it...its a couple days past the 15 day return policy. If not, I'll have to ship it to Tokina (three year warranty). Do you think this is something they can repair. Also, I tried all the suggestions out there: clean the contacts with an eraser, remove battery and card, etc....
Help!