's romance with ex-girlfriend Scarlett Johansson
almost put his role in movie 30 Days Of Night
in jeopardy - because she gave him glandular fever.
The 29-year-old struggled to film scenes in the vampire picture after contracting the "kissing disease."
He says, "I was falling apart because I had glandular fever, otherwise known as the kissing disease. You're supposed to have it at 14, so apparently I haven't kissed enough people."
And the actor was further plagued by a handful of injuries while filming.
He adds, "I broke a knuckle, ruptured a blood vessel in my eye and kept getting beat up with cuts and bruises. It was a trying first month."
Hartnett and Johansson dated for a year after meeting on the set of movie The Black Dahlia
, but split in November last year.
(This news article provided by World Entertainment News Network)