These cycles remain unexplained, and they are inadequate to explain ice ages.
The cycles are, however, observed. They do fall out from the Kepler and Newton equations for orbital motion- they are not mysteries.
The periodicity of the cycles does correlate rather well with glaciation cycles over the last 700 ky, but not perfectly. It seems odd that insolation changes brought about by observed orbital elements would NOT influence climate.
There's lots of stuff written on the topic, much of it online now.
http://en.wikipedia.org/wiki/Milankovitch_cycles