Follow the procedure as outlined above by abu but also delete the complete crossepg folder, it will be recreated with a fresh database when crossepg downloader is run.
I'm not sure why ppl just concern themselves with the epg.dat when dealing with crossepg as problems are usually in it's database stored in the folder from which the epg.dat is produced.
A corrupt crossepg database will produce a corrupt epg.dat so best start with a fresh database.