We study the aging of a colloidal glass, which is obtained for extremely lo
w volume fractions due to strong electrostatic repulsions, leading to the f
ormation of a "Wigner glass". During the aging, a new crossover between a c
omplete and incomplete decay of the correlation function is observed, accom
panied by an increase in the non-ergodicity parameter. The dynamics can be
described as a cage-diffusion process. For short times, the escape of the p
articles from "cages" formed by neighbouring particles dominates; for long
times the particles cannot escape anymore and the system becomes strongly n
on-ergodic.