
The ex-couple (plus Richie's new GF) reunited Saturday night at a hotel in Westlake Village, California to celebrate Ava's 11th b-day -- and though their Denise Richards-riddled split was rough, everything surprisingly looked A-O.K.

Heather has so much class that Jack was probably spending time with his boys. I thought Ava's birthday was 2 weeks ago.
I live in Westlake Village and see celebs all the time, however I never see the PAPS. Ironically, I've seen Heather at my gym, Richie and Ava at Blockbuster and Denise at an ATM !
Britney Spears might miss a lot more 'X Factor' auditions ... because she can! Simon Cowell gave Brit damn near free reign in order to sign the pop star to that $15 million deal -- but is it backfiring? We'll tell you what peeps on the set are saying.Plus, Chris Jericho's…