According to sources for Australian tabloid, NW, Heath's work in the new Batman film - he's playing the Joker - may be the cause of their rift. Ledger has been incredibly stressed from filming, says one insider. The snitch revealed, "Michelle thinks Heath's just under too much pressure and taking the role too much to heart. She's been trying to urge him to take a few months off from filming, but he refuses."

Heath's moodiness has even caused him to put off his marrying Michelle indefinitely. Another source adds, "Things between them are the worst they've ever been."