Due to wear, high usage vehicles can experience ignition lock and tumbler failures. The ignition lock cylinder will generally require replacement to correct this concern.Google+
Car Problem Reports
Mercedes-Benz SLK230 High Usage Vehicles May Experience Ignition Lock and Tumbler Failures
Mercedes-Benz SLK230 Problem
Average Mileage: 94,564 mi (64,000 mi - 137,648 mi)
Visitor, 2003 Mercedes-Benz SLK230, 126,000 mi
Ignition stuck; key will not turn
Visitor, 2003 Mercedes-Benz SLK230, 85,000 mi
The key will not turn on the ignition. Had to replace tumbler and sterring lock.
Visitor, 2002 Mercedes-Benz SLK230, 70,000 mi
replaced cylinder lock.
Visitor, 2003 Mercedes-Benz SLK230, 137,648 mi
Had them replace ignition Lock and Tumbler
the key is hard to remove
Visitor, 2004 Mercedes-Benz SLK230, 79,000 mi
the key will not turn , it will go one click and sticks so that car cannot be started