You can upgrade the temple if it is of the same type (not necessarily the same name). Look in the files for the exact ones and note that if a Roman faction captures a Sacred Circle of Epona that they can build it up to Pantheon, but only if it is already a Sacred Circle. This is really awesome because you can get +5 experience from there, so you can train Praetorian Cohorts with 2 Silver Chevrons and Gold Weapons and Armour if you are the Scipii. They will take just about anything out.
As to the original question, I think it's one of the minor bugs. Try downloading Bug Fixer, which makes the game much better to play by eliminating most of these. Alternatively, it's one more word to add to export_descr_buildings.txt if you want to fix it yourself.