Willem-Jan Markerink notes on the EOS mailing list that there is a EOS EF L 24-105mm recall. This is newly released MSRP $1249 prosumer lens that is attracting a lot of interest from photographers such as Fred Miranda because of its compact size and stellar optics. From his posting:
EF 24-105mm RECALL
According to Canon USA, there is a problem with early production
units of the EF 24-105mm f4L IS USM lens. There is an unacceptable
level of flare in certain conditions, most noticeable at the wide
zoom and wide aperture settings.
Only lenses with a serial number under 1000 are affected. You will
find the number engraved on the rear of the lens. It is not always
easy to see - we find that it helps to shine a light at an angle
across the rear of the lens to increase the texture, and use a
magnifying glass. The number is prefixed by 'UT' (which indicates the
factory of manufacture).
If you live in the USA, starting 14 November 2005, Canon will repair
free-of-charge, any affected lenses. Other countries have yet to post
information, but check their web sites over the next few days, or
contact your local Canon Service Centre.
Rob Galbraith has an article on the recall. If you can read Japanese, there's a post on DCWatch too. I'm disappointed, I hope this isn't indicative of Canon's sacrifice of quality of control standards in the face of a rapid product development cycle.
I would avoid buying one of these lenses unless you can get a guarantee that the serial number is greater than 1000. It's not worth the hassle of having to ship the lens to Canon for the (free) repair -- and repaired lenses sometimes don't perform as well as new ones.