Yay! Solved it. I compared the SD card to what Jeti's site says it should have. Mine was missing the "voice" folder but has a lot of corrupted files dated 1986! I copied the "voice" folder from jeti to my SD card and now the announcements work again. The emergency shut down must have exploded and corrupted the original voice folder. Think I will copy all the other folders too just in case anything in them got corrupted.
Problem sorted, thank goodness.