How to remove plastic strain relief connector?

I'm replacing a bathroom wall-heater. To replace the wall can, I need to extricate the house wiring from the old can, but cannot easily remove the strain relief connector in the knockout. [The type I have is shown at this link: http://www.grainger.com/Grainger/THOMAS-BETTS-CableCord-Connector-3LK42?Pid=search]

How is this usually done without damaging the house wiring?

Thanks,
Annette

There may be an easier way, but I've taken them out by using pliers on the inside...squeeze the locking tabs and jockey it out of the hole.

Thanks. I had figured this out just after posting.