Mischa Barton caused some trouble at Halloween party this year

New Yorkers have been seeing rather more of Mischa Barton than they bargained for in recent days.

Mischa, who's in town to shoot scenes of "Law & Order: SVU," is wearing very little in her role as a hooker.

Bitchy sources are saying that Mischa (above, on set) kept forgetting her lines while filming with Chris Meloni and Mariska Hargitay.

But c'mon guys, the girl only had seven lines, how could she forget them?

The same sources say it's because Mischa's been rocking out all over the Big Apple.

"She's a regular at Antik," one source said. "She usually comes late every Thursday and leaves late. A lot of times she'll even go to another club after she leaves."

A rep for Barton pooh-poohed the partying reports saying that everything was going "swimmingly."

But the tittle-tattles point to Mischa's well-publicized battles with substance and alcohol abuse.

She was admitted to hospital in July after a so-called "drug- and alcohol-fueled meltdown," after spending time earlier in rehab for a DUI in Dec. 2007.

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