Problem with iPhone Dock Connector Cable 3G

I purchased an iPhone 3G in December and last week I looked at my connector cable and saw bare wires poking through on the phone connector side. I took it back to the AT&T store where I purchased it and they promptly replaced it with no questions asked. A week later, I notice the same thing happening to the new one. The insulation on the cable appears to be too soft and when they mate it with the hard part of the connector, it starts coming apart from flex. Since there is no strain relief, I suspect it will happen again. Anyone else with this problem? Any solutions besides wrapping it with electrical tape?
Thanks, Tony