Thanks for the sample, I downloaded it without any problems.
As it turns out, I should have tested this with a 5D CR2 sample instead of a 20D sample, because the 5D also has these two large tags too. (I'm surprised no 5D owner has complained about this yet.)
I've scanned through all my sample EOS JPEG images, and tag 0x4002 exists in some of them, but 0x4005 does not. So I think it is safe to just drop tag 0x4005 when copying all tags to a JPEG image. This will allow the EXIF information to fit in a JPEG segment.
ExifTool version 6.08, just released from
my web site, incorporates this modification. It should solve the problem you observed.
Thanks for bringing this problem to my attention, and for providing a sample image.