A. There are at least two possibilities. He could be operating on autopilot, going about his business just as he did while you weren't around. Or it's payback time -- he's giving you the cold shoulder for having had the audacity to leave him. In either case, the fact that your persona non grata status ends proves that your child still loves you (obviously) and that you're back on his radar screen.
Kids who act this way about their parents' homecomings often have trouble making transitions in general. Routines and rituals help. So try to get home around the same time each evening. Preschoolers can't tell time, but they know when you usually get home (after Dragon Tales, before dinner). Of course, on work trips you can't guarantee exactly what time you'll be back, but you can provide an ETA. While you're away, talk to your son on the phone (if he'll get on) or e-mail him. Bring him a little present from your travels -- not to buy his affection but because it shows you were thinking about him and because it's just fun to get stuff from such exotic places as New Jersey.
When my girls were smaller, we had a couple of home-from-work rituals that instantly switched us to family time. With Madeline, it was "roly-poly girl," in which we'd roll around on the bed, locked in each other's arms and laughing. Ellie would put her hand out and ask for my earrings, as if to defrock me of my work attire, and then sit on my lap in the rocker and examine them. The parent-child relationship is one in which problems and concerns can, over time, mellow into nice memories. I hope yours will too.
Trisha Thompson is a contributing editor to PARENTING and a former editor-in-chief of BabyTalk.