I just had someone say this to me. I'm pretty sure I know what it means already but I came here to confirm if I'm correct or not.
こんにばんは is a combination of こんにちは and こんばんは.
こんにちは is what you would say if you meet with someone for the first time or if you already know him/her, when you meet them while going about your daily business. こんばんは is similar, except said during the evening.
こんにばんは is what you would say if you meet with someone new for the first time at night.
Is my guess correct?