[aruanan]

The observed electrostatic rotation was not expected and could not be explained by available theory.

PINK MATTER ALERT

[Gary Boldwater]

It can be explained by current knowledge (forgive the pun). The field of an isolated charged conducting sphere is circularly symettric and the charge is on the surface. It experiences no torque.
In the presence of the other spheres the field is no longer circularly symettric. Forces are experienced by the sphere, causing rotation and probably pendular displacement.
The simplest example of this is an electron above a flat metal plate. The field of the electron is no longer circularly symettric. Because of this, it tends to move toward the plate (by induction of "positive" charge density on the surface of the plate, "positive" meaning less electrons in the vicinity).
If the net lines of force on a charged object are not symettric, the object will go into motion to try and make the field lines symettric through the motion. This is more apparent with materials that have less charge mobility.
The rotation rate is inversely proportional to the conductivity. The greater the conductivity, the faster the relaxation time of the material (the quicker charge can redistribute on the surface)and the less torque it experiences.

The rotating spheres do create a magnetic field.