MH Lighting help, please!!!

[Seriak]

I just purchased a 175 Watt MH bulb and it worked great for about a month. However at the one month point it didn't come on one day. Well I thought it was defective and asked the supplier about it and they said to send it in to them and they will test it and if it was defective they would send me another one. Well that is fine by me. Well the next day the light did come on and it worked for the next few days. However yesterday it didn't come on again. Has anyone experienced this before. It is a 2 MH setup and the other bulb comes on fine everyday and has for the last 2 years.

Chris