I had the same problem with mine all the time. I eventually removed the ignition switch and took it to a locksmith who cleaned it up as best as he could. The switch still sticks in on occasion. I just giggle or tap on it to get it to pop out, then my key will turn in the switch.
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.