You have a thermo problem. Sometimes, the lamp will do this also if it has many hours on it.
Here's what I would do:
Let the lamp cool down. Remove the electric. Remove the bulb. Look on the base of the lamp to see if it had a poor connection. You can tell a poor connection by the solder looking splattered or greenish/black. Look at the socket for any black/blue tracking.
Get back to me with your findings. Also old lamps will do this.

rosemallow,
thanks for your response. i removed the bulb and looked in the socket and didnt see any splattering or discoloring. it looked very new actually. is there any where else i can check to see if this is the problem?? thank you for your help.

(Lermer) "Future Brite" is not the best e-ballast; Life Light is. Probably there is a thermal switch in the ballast that turns it off if too hot; this switch (or something else) might be faulty.

I install more HP lamps in my business than ballasts for lighting. 95% lamps installed as to 5% ballasts for HP.
Because of the base up for lamps the socket takes a beating.
You did not say how old tha lamp was.
I am not sure about what ballast is better or worse.
I don't want to make you spend money, but I would change the lamp first.

thank you again for your help. i talked with future brite and through trouble shooting and your help we have decided it is the lamp that is faulty. so i need a new one.

being new to growing with lights what do you reccomend. i have a 600 watt ballast. the guy from future brite told me not to exceed 120volts. i am growing a variety of vegetables. tomato, lettuce, peppers, herbs and some flowers. can you help me decide which lamp is right for my needs before i drop a lot of money on one. the one i was using before was a hortilux super hps. thank you!

I have a black diamond led grow light perfect sun it keeps shutting off. If I mess with the switch a bunch it comes back on . I just got mad and punched it n it came back on . I think I hv a bad switch or short. Anyone else have this happen?