See today’s earlier entry. Persistence pays off, with a different Canon support engineer taking the time to research and answer my query. This is what I had expected, and I’m glad it happened, though the answer is not necessarily a happy one for the 5D. Note that the original tech-support dweeb gave me an answer in direct contradiction to the subsequent response—Canon had indeed tested and known that cards up to 8GB were the limit.
Thank you for your reply. We value you as a Canon customer and appreciate the opportunity to assist you with your EOS 5D.
According to our tests, only memory cards up to 8GB are supported. This has also been confirmed by SanDisks tests https://www.sandisk.com/Compatibility/Device(8208)-Canon-EOS_5D.aspx.
As of today, Canon USA has made no announcements regarding the development or release of a firmware update related to the issue you have described. This does not mean that a firmware update to support 16GB is not in the works.
We hope this information is helpful to you. Please feel free to contact us again if you have any other questions or concerns.
Thank you for choosing Canon.
Technical Support Representative
So it looks like it’s just a waiting game with the 5D. Now to ask Nikon how the D200 will handle the card...