The Luminous Landscape compiled a list of failures amongst nearly 80 photographers on their Antarctic Expedition. The results may upset some brand loyalists.

Here is a summary of their findings:
Conditions faced were light rain, temperature hovering around freezing (-3C to +2C), salt spray, so not exactly extreme conditions.
77 Photographers and Instructors went, so a lot of gear.
About 70% shooting Canon, 30% shooting Nikon, one Sony user, ten Phase One backs.
Sony A900: They took two plus seven lenses, performed flawlessly.
The Canon EOS 5D Mark II lent to them to test by Canon failed on the first day ashore in rain.
Canon 5D Mark II's were hit the hardest - six failures out of 26 cameras (almost 25%). After warming up/drying out three recovered, three didn't. All appeared to be water/humidity damage. Two of the failures were using Kata rain covers in light rain.
Several reports of water collecting between the battery grip and base on the Canon 5D Mark II.
A Canon 1D MKIII kept reporting Error 99.
A Hasselblad reported electronic lens connection problems.
Two Canon G9's failed.
No Canon G10 failures out of approx 30 that went on the trip.
A Nikon 80-400mm lens came apart.
No Nikon bodies (mostly D700s) failed in any way.

Luminous Landscape has much more information, including some specifics of the failures and the conditions they happened in at the link below:

http://www.luminous-landscape.com/essays/antarctica-2009-worked.shtml