Investigators looking into the real reason behind the Jessica Simpson/Tony Romo breakup have hit another dead end, as their main lead, Kenny Chesney, has flat-out denied that he contributed to the relationship's untimely end. The country singer had been the investigators' biggest suspect when rumours surfaced that Simpson flirted with Chesney at his Fourth of July party, while Romo looked on, fuming.

Not so, says Chesney.

"Tony's a friend, and I wouldn't flirt with a buddy's girlfriend," Chesney told People. "More importantly, Jessica was just being sweet and there was nothing else to it. It's not funny. There were no problems. Everybody got along great. After the party, everybody went their own way and nobody thought anything more about it. Period. End of story."

Simpson and Romo, who had been dating on and off since 2007, broke up a mere five days after the party, but Chesney insists this is just a coincidence.

"If a girl and her boyfriend can't go to someone's house for a Fourth of July party and talk to the other guests without it turning into a big nightmare, then I feel really sorry for Jessica and Tony, who're both really nice people," Chesney added.

Chesney's denial is a big setback for investigators, who have been scrambling to pin blame for the breakup on someone – anyone – so that the concerned public can finally rest. It will be weeks before DNA evidence will be processed, but if the results are inconclusive, we may never truly know what happened.

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