This sounds like (pun intended) an interaction between the carriage bearings and the guide bar or bars. This issue may go away after the bearings/bars have had an opportunity to break in, but then again it may not go away. I would ask HP to replace the product. Bearings and their lubricants are delicate issues and it doesn't take much to cause problems.

When I went to Lincoln, NE to compare the B9180 with an Epson R2400, one of the first things I noticed was a noise similar to that. The shop I was at had 2 others in boxes they were waiting to setup for their own photo printing. It was decided to unpack and hook those up and give them a good workout. Both of the other printers also had the same noise. They were looking at returning the one they were putting out on the floor for customers to use for photo printing and most likly returning them all in favor of Epsons. Based on what I saw, heard and compared between printing results, I went with the Epson to add to my Canon dye printers. I would say it is a common problem based on those 3 printers and HP's response. Of course, it could belimited to a certain day's production run too. We isolated the noise as coming from the print head mechanisms also.