Something is definatly not right. Unfortunatly I can't tell you what it is.
What do the E-mails from cron tell you? They should give a clue as to what the problem is.
With out more information it is almost impossible to help you figure out what is wrong.
Personaly, if I had that happening I would back up my data and start over with a clean installation. But then I am kinda a newbie, so I take the easy way out.