Thanks for everyone's help so far. Yes, I know the *outer* side of the lens will fog when going from cold to hot or humid or vice-versa, and this part is correctable with wiping until the camera adjusts, but it's the inner side of the glass that has been the problem.......and the thing is, is that I was totally not expecting it to happen on Saturday, since I got to the track at 7am, took some pictures (before security told me not to) of early am horses in training, as well as some front shots of the track entrance.

It was not cold, not hot, since I had been up that morning (had spent 2 hours on a PA bus from Philly, and 8 hours before that on a Greyhound bus from NY. And before that it was in my apartment, which has no airconditioning at all.

So after 7am I put the camera back in the bag where it sat around (outside the track) doing nothing until 9:40am, when I went back with the owner to the stables. I took a whole roll of her horse with the Canon lens without incident, outside the barn, then led her horse back in the barn and stood there for a while, then went outside and up a flight of stairs to the track. If it wasn't around my neck it was in my bag, and the bag itself had been in external and/or non-drastic elements for at least 3 hours.

The bag has not been subject to any downpours lately. And, the lens was fine with the first roll I shot. There was no discernable temperature change from climbing one flight of stairs to the track. It was breezier up there.

So, there's probably some damage, huh? (sigh) And I should send it directly to Canon? How much does this usually cost, anyway? Someone mentioned a breach--is this only caused by very hot temperatures? I have never left it outside for several hours in direct sun nor in a hot car (don't have a car, actually). I have been out for hours at a time, but it is usually in my bag, or, around my neck for extended periods if I go to the zoo (but then I am usually using my 100-400 Phoneix almost exclusively)

Thanks,
Vanessa