  We present the results of a multi-epoch observational campaign on the
mini-broad absorption line quasar (mini-BAL QSO) PG 1126-041 performed with
XMM-Newton from 2004 to 2009. Time-resolved X-ray spectroscopy and simultaneous
UV and X-ray photometry were performed on the most complete set of observations
and on the deepest X-ray exposure of a mini-BAL QSO to date. Complex X-ray
spectral variability, found on time scales of both months and hours, is best
reproduced by means of variable and massive ionized absorbers along the line of
sight. In the highest signal-to-noise observation, highly-ionized X-ray
absorbing material outflowing much faster than the UV absorbing one is
detected. This highly-ionized absorber is found to be variable on very short
time scales of a few hours.
