Avril Lavigne's fourth album, being produced by soon-to-be ex husband Deryck Whibley, was supposed to be released last November. Now Lavigne is saying the release is expected in ?early 2010."

But a source says it could be more like mid-2010 because the two young Canadians who moved to Hollywood four years ago, got married and then separated, can't stand working with one another and are finding it ?terribly frustrating" to finish the last few songs.

It was Lavigne, 25, who filed for divorce in September after three years of marriage to the 29-year-old Sum 41 musician, citing irreconcilable differences.

Things heated up in November when Whibley's lawyer insisted that spousal support be included in the agreement, but Lavigne's attorney countered she wouldn't pay it.

The gloves are off in court ? superstar Lavigne, who also has a fashion line, is worth lots and lots of dough that will have to be, under California law, divided fairly with Whibley as he has played a key role in her career.

The pair are trying to come up with a compromise production schedule to get the acoustic album, tentatively titled Pink Crust, to market.