Radisoty is rendering method that simulates global illumination. This lighting approach mimics realism perfectly. In Awakening radiosity uses 3D accelerator hardware to improve performance. This  may case you CPU not full work when compute radiosity lighting; The advantage of this unique method is obvious: it saves a lot of time computing radiosity solutions for large scenes compared to the usual pure-soft algorithm.

lighting leak: near pillar, set pillar's four side surface to Double Sided to avoid this. Also, there is a Double Side Rendering option in Light Map Option dialog.