The problem ceased to exist after I started using a straight razor, requires a little more work (sharpening, stropping etc.), especially with the sweet Lemmy Chopstache I've got going, but it's worth it to me. I've been told the same results can be achieved with safety razors, the logic being that a single blade is less aggressive and irritating to the skin than the action of having multiple blades going over your skin in a single pass, that, and you have more control over the blade angle and fewer passes to get the desired shave.

EDIT: Also, have you tried keeping a warm/hot wet washcloth over the affected area before shaving? Other than being continual irritation, there could likely be an ingrown hair issue as well, usually the effect of a too-close shave, the washcloth, in lieu of hot lather, helps to bring the hairs out.