I was sort of being a smart*** but this did just happen to me recently and I understand this is a common one. Apparently 50% of bike noises come from QR's based on my wholly unscientific survey of BF responses (the other 50% being unruly bits of kit striking things)

I figure too loose would be the problem - in my case, I had a tick noise once every pedal revolution that I figure was chain tension causing the wheel to pull out and then fall back into place. I tightened the QR and it was gone, happily.

I also had a terrible creak coming from what I though was the head tube/headset. I was convinced my overtightened quill stem had bulged the steerer tube and no amount of lubing, tweaking, shimming or swearing would help. I tried to tighten the quick releases and that did not work. I was ready to buy a new fork, headset, and stem...and then I determined that it was my saddle.