I'm replacing a light fixture in my bathroom. It's a single light ceramic socket sticking out from the wall with a glass globe cover. It's hooked up to one switch along with an exhaust fan. Both the fan and light turn on an off by the single switch.

My problem is that the new fixture when connected doesn't work. Turning the switch to the off position the light is dim and the fan doesn't work. When turned "on" the light is bright but the fan still doesn't work. I've tried both single-bulb and two-bulb fixtures with the same results. I've hooked up the old light again and it works fine. Any ideas?