light bulbs keep burning out

[marke]

i have a ceiling light fixture that i installed myself about 2 years ago. a few weeks ago i replaced a bulb (it holds 3, 60 watt bulbs) that had burned out. it burned out again in less than a week. we took the fixture off the ceiling and the metal bracket in the ceiling looks rusted, and a couple wires looked melted in a couple spots. we got rid of the bad spots on the wires and put a new bulb in (we were using standard 60 watt bulbs, apparently the fixture requires 60 watt "bm" bulbs, so we put those in) a week or so later, another bulb burnt out. what is causing our problem, was it because of the wrong king of 60 watt bulb we originally used (for the last 2 years) why does the bracket look like it is rusted? is it "burnt" from too much heat? we are planning to replace all 3 bulb sockets. what caused our problem and what should we do?

[John Nelson]

If you want to know whether it's the bulbs or the socket, next time one burns out, move one of the other bulbs into that socket and put your new bulb into the socket where the good bulb was.

[marke]

thanks for the response, we changed out all the sockets and the bulbs have not burned out yet, but its only been 3 days. what i really need to know is why the bracket looks like its rusted, there is no water source near our ceiling, its on the bottom floor of a 2 story home. and does it harm a fixture by using standard 60 watt bulbs instead of the 690 watt "bm" bulbs required by the fixture. does this cause excess heat, which in turn caused my problems?