*sigh* its not interface/driver related. I have the same problem with my EMU card, and every other interface I have used, the speakers you use to monitor have magnets, they put out and electric-motive force (EMF), guitar pickups, create/send EMF signals based on the reaction of the strings and other freefloating EMF signals, including anything with an AC transformer such as a computer, a guitar amp, a TV etc and Radio frequency transmitters such as Cell phones and Radios. Get near that EMF and your pickup will "pickup" that signal. Unshielded instrument cables can pick them up to, therefore if the headphone cord was touching the cable, that could cause the problem to. Most liekly though, if you turn down your monitors when you track and the crosstalk gets lowere in volume or goes away, chances are it was your monitors being too high in volume.
If I believe correctly, most headphones don't have insulation, just like speaker cables. Thats basically what headphones are, personal output speakers.