Although Arquette, 40, filed for divorce in January from actor Jane, they're still close pals—and possibly headed for a reconciliation.

A source tells Celebuzz that Jane held a belated 40th birthday bash for himself at Los Angeles nightspot Hwood on Friday, where Arquette happily attended in tow with her brother David and his wife Courteney Cox Arquette.

"Thomas was so doting," the source says, "there were a ton of people at this party and it was obvious where his attentions were."

Although Jane supplied partygoers with a full bar, he opted for Morrocan tea, shuffling barefoot around the private event space, checking in on Patricia frequently.

"It was more than just being civil to an ex," said our source, "they look like two people working toward something."

Arquette and Jane share a daughter, 5-year-old Harlow. While Patricia has requested sole physical and legal custody in the January 5 divorce documents, neither spouse is seeking financial support.

Arquette currently stars on NBC's Medium. Jane will next appear in HBO's Hung, an original series about a high school basketball coach with an extra large gift.