This is an extremely common problem on Kenwood head units featuring the "Mask" feature. There is a small ribbon cable / flex PCB that attaches the faceplate to the main circuit board. After rotating several times eventually one or more connections in this ribbon breaks.
I no longer remember the URL, but do a google search under the Kenwood deck KDC-X717. Someone has posted a step-by-step tutorial on how to reapir this. It is a fairly simple task, with no soldering required. Just some tools, dexterity and a little patience will get you through it no problem yourself.
The new part is fairly inexpensive at around $10-15, and once repaired the units should give you another several years before failure. Check Kenwoods homepage for contact info on where to obtain parts through www.kenwoodusa.com
Hope this helps.
Bryan
February 2005