After a power cycle, ArcSystem RDM fixtures lose their settings and return to factory defaults (DMX address 1, single cell mode, minimum level 99%). This may result in one or all cells being stuck on. This is a bug present in ArcSystem RDM 1.0.0 and 1.0.1. Updating your fixtures via Updaterator to 1.0.2 will resolve this problem. If updating is not possible, using Net3 Concert to reset the fixtures to defaults will temporarily resolve the problem until the fixtures are power cycled again.