dual dimmer switch for two tree bulb halogen lighting strips?

dual dimmer switch for two tree bulb halogen lighting strips, only one of the lighting strips is working, bulbs are all fine, have checked switches and wiring appears sound, also another light on the same circuit has stopped working. While 2 of the 4 lights on the same circuit work, while the other 2 dont ????
There are two lights in the kitchen( the halogen lighting strips), one light in the hallway operated by a normal switch, and one light in the lounge operate by a dimmer, all switches and lights are no older than 18 months old. One of the kitchen lights and the lounge light have stopped working. Light switches and lighting strips all bought in Homebase UK

Idal
November 2008