Sounds familiar....

I bought a brand new Giant OCR2 a few weeks ago and had it out on the roads yesterday. Ten miles out I too had a crank creak that stuck with me the whole way home. To play it safe, I took it into my LBS (where I bought it) and had them check it out. It turned out that the crankarms (I believe) hadn't been fully tightened. In the process of fixing that, the crank spindle itself broke.

So...it might not be a big problem in your case, but my particular situation went from what I figured would be perfectly innocuous to pretty severe, simply because I had someone with the tools & know-how take a look. Also, FWIW, consider that these are both Giant bikes in question.

Cheers,

- Mark