"I'm listening, what is your problem?"

Translation: Je vous écoute, quel est votre problème ?

[JoBorn1]

should it not be I'm listening to you

[Sucy-en-Brie94]

Je t'écoute, quel est ton problème. Accepted :)

[RoslynJS]

"What's your problem?" sounds impolite or even sarcastic in English.

Less personal: What is the problem? What's the nature of the problem?

[Harvey686037]

"J'écoute"also accepted