It really depends on your in-camera settings and workflow, in my opinion. With in-camera sharpening, this is a fairly common effect, and easily demonstrated on some of the more extreme sharpening settings available. Regards workflow, it depends on your processing. Using the Shadow/Highlight tool in Photoshop is a major culprit, as is Sharpen as opposed to carful use of Unsharp Mask.
If I am teaching grandmother to suck eggs, do stop me, otherwise, a good sample workflow is available from Jid
's site here: http://www.jid.me.uk/workflow/
It's worked for me every time, quality-wise, and it makes a great deal of sense, too.
In any case, good luck, and keep us all posted!