Replace broken 15-85 or move to 24-105?

See if Amazon (if you bought it there) will take back the old one for an exchange. If you're a good customer they may do it.

They took back a four year old lens of mine once and gave me a new one. They didn't like Canon's cheap one year warranty. Great customer service.

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Grizzly bears of Glacier National Park
http://www.parkcamper.com/Glacier-National-Park/Glacier-grizzly-bears.htm