Jessica Simpson

Jessica Simpson, John Mayer Reunite in NYC

05/21/2007 at 05:15 PM EDT

Jessica Simpson and John Mayer have gotten together ... again.

The off-and-on couple reunited in New York City on Sunday night, sources close to the situation tell PEOPLE.

"They saw each other last night. I have no idea what will happen with them tomorrow," says one source. "I don't think they're sure. All I know is that they like each other and saw each other. Everyone's waiting to see what's going to happen."

A source close to Simpson chalks up the couple's recent break to the usual romantic ups and downs.

"They're in a normal relationship," says the source. "This happens with relationships sometimes."

Adds the source: "They went on a date last night. They had a great time. They had dinner."

On Friday, multiple people familiar with the couple confirmed that Mayer and Simpson had split up – but predicted that it would be a temporary break.

One friend said last week that the pair had "been emailing and talking to each other" since Simpson went to the Cannes Film Festival in France last Wednesday, adding: "I'm sure they'll get back together."

Reporting by KC BAKER and MARK DAGOSTINO