New lens acting up. Solutions?
 

http://img13.imageshack.us/img13/3450/img9119m.jpg

Body: EOS 500D/T1i
Lens: Tokina 12-24 f/4 DX II (Purchased from ebay, recently)

It works perfectly fine at F4. After shooting at F4 for a really long time, then switching it to F8 (or any other aperture), it will focus properly but go dim after you press the shutter down completely. The message shows up on the rear LCD screen. If I remove the lens and install it back again, the message doesn't show up for maybe a few more days.

What could be the issue? Everything looks clean.
I have maybe 500 shots on this lens now.

Clean the lens contact.

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okay just joking, but really, try that, perhaps it'll go away. if not then... dunno.

haha, that's probably not too far from the truth. My Canon 17-55 did that and cleaning the contacts kinda worked. Then the IS crapped out about a month later and I had to send it in to Canon to repair.

Sounds like a lens issue...unfortunately, maybe that's why it was being sold on e-bay.