I know this has come up before, your best bet would be to do a search, as I can't find the thread at the moment.

Q: I'm getting following Error after installing EB:
Script Error in data/descr_event_images.txt at line 623, column 1
Unknown event string faction_defeated_by_player
what can i do?
A: This is possible caused by a bad/corrupted download file, you have to download EB again