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Ex-spouses Avril Lavigne and Deryck Whibley both found themselves at Trousdale last night after Avril performed at the Race To Erase MS event in Century City.

Compounding the awkwardness was the fact that both Avril and Deryck showed up with new loves -- Avril was with boyfriend Brody Jenner and Deryck had a new girl on his arm!

Add to that the fact that Paris Hilton (who dated Deryck before he married Avril) was also at the club and you've got a love quintuple!

Other celebs who were at Hollywood's hottest spot last night were Katy Perry and Russell Brand, Hilary Duff, Nicky Hilton, Apolo Anton Ohno and Sophie Turner (gallery below.)