Express o nly connects w/cord

This isn’t a dealbreaker yet, but my new Express has a strange problem: when I plug it in directly to a computer USB port, it charges but is not recognized by the computer in any way (even when I tell it to look for new hardware). If, however, I connect through the stubby USB extension cord that it came with, it connects and works fine. This happens on 3 different computers, all with up-to-date XP home. Any suggestions (other than carry the cord whereever I go)?