Thanks for the reply. I have only modified the top image in the theme and nothing else. I have the following plugins installed:
NxtGen Gallery
Yoast WordPress SEO
Akismet
Share and Follow
All are presently active. When I left home for the cycle trip, I never had enough posts to test the archive feature, so I am unsure if any of the plugins may be guilty? Not having regular access to a computer will make deactivating and reactivating a little tricky.