I have a very simple/cheap set of gaslogs. To light the pilot light I
turn the control knob to pilot, push the knob in and press the
'sparker.' Hold the control knob for 15 seconds, and then can turn
the control knob to turn on/regulate the flame.

The set of logs is only a year old. All of a sudden I can light the
pilot, but the control knob won't turn. It is absolutely locked.

I suspect it is some kind of safety catch that is malfunctioning.

Any thoughts or ideas are greatly appreciated.