I'd be looking in this direction first! Cam covers have been off.....I'd have probably bought a new one to save hassle!
Though the crank bolt is a good shout.....surely when you're doing timing belts often you wouldn't forget something like that! Imo that's a pretty serious mistake! Anyway.....don't you love someone posting and never replying again after helpful ladies and gentlemen like yourselves take the time to give a reply!