Mischa moved out of the West Hollywood building in which she had been living ... this after a meltdown caught on video which resulted in her hospitalization late last month.

The 'O.C.' star put all her stuff in the U-Haul and drove to another WeHo building right below the Sunset Strip, but she misjudged the height of the carport and the top of the U-Haul slammed into the overhead support.

She was clearly shaken after the crash, saying everything she owns is inside the vehicle.

It's a little weird ... she moved out of her old apartment Wednesday but it seems she was driving the U-Haul around town for several days before landing at her new digs.

Mischa's old neighbors had complained she was disruptive to the point cops were called every few months.