Ever had a friend who seemed unlucky in love but in actuality just had a tendency to date the wrong people? Seems some of Jennifer Aniston's pals may be smacking their heads in frustration now that it appears her weekend of snuggle-bunnies with indiscreet ex John Mayer wasn't just a one-off.

The Chicago Sun-Times says members of the always-well-coiffed star's inner circle, including BFF Courteney Cox, are "upset" that she's reunited with the short-attention-span crooner two months after their tabloid-topping implosion.

"Jen's friends are just worried that she will again be hurt by John," a source tells the paper. "Granted, this isn't as serious as what happened with Brad [Pitt], but it's a shame she's attracted to a guy you know is not around for the long haul."

The mole even has an expiration date picked out for the resurrected romance, predicting Mayer "will have moved on to someone else by Christmas."

Ouch.

For now, they appear to be very much back in the wooing phase. On Wednesday night, Jen, 39, was reportedly on hand as John marked his 31st birthday.

The celebration took place at a swanky, members-only cigar bar in Los Angeles, where they chilled on a patio and Mayer was seen stroking Aniston's silky mane, says Us.

"They seemed to be having a great time," a bystander blabs to People. "They were sitting next to each other. They're a very good-looking couple and seemed happy together."

Meanwhile, Us reports they also enjoyed a "romantic dinner" Tuesday night at the bar of Los Angeles' Sunset Tower Hotel, although "romantic" might be a stretch, considering a trio of pals joined in on the chow-fest.

For you celebrity foodies out there (and you know who you are), the yoga-toned actress ordered what the mag calls her usual -- a grilled chicken salad -- and shared a bottle of wine with the group.

The carb-light lettuce, poultry and vino combo apparently acted as some sort of aphrodisiac for Aniston, because she and Mayer were acting oh-so-couple-y during the meal.

"They looked like they had the best time," says a spy. "They were holding hands at one point and seemed very much back on."

Adds the eyewitness-cum-body language expert, "She seemed extremely happy to be back with him. They were close and laughing the whole time with their friends."

After the meal, the fickle flames attempted to make a quiet exit out of a back entrance of the hotel, but they weren't quite stealthy enough to avoid lurking paparazzi.

Jen cozies up to BFF Courteney Cox at the Glamour Reel Moments event in Los Angeles on Oct. 14. (©WireImage.com)

Their cozy meal, which followed Jen's appearance at the Glamour Reel Moments event to support a short film directed by Cox, follows similar lovey-dovey sightings from last weekend.

On Friday, Aniston and Mayer reportedly enjoyed a "very public date" to a Ray LaMontagne concert in Boston before moving on to New York, where they were spied downing oysters at an Italian eatery.

By the time they landed in Los Angeles on Monday afternoon, they were supposedly hugging and sharing "a long, lingering kiss."

It remains to be seen whether love will be lovelier the second time around for the twosome, who, according to Mayer, just weren't a good fit.

"I ended a relationship to be alone because I don't want to waste somebody's time if something's not right," he announced in August during his infamous post-breakup babblefest. "People are different, people have different chemistry."

According to Us, they remain in very different places in their lives -- and it hints that compromises are already being made.

"She is going with the flow more," a source tells the mag of Aniston. "She's willing to hold off on her old priorities."

Mayer, meanwhile, "wants a child one day, too. He just doesn't want that this second," adds the mole. "They have different goals, but right now, they're just hanging out again."