My 27" magnavox keeps shutting off

Hi i have this TV for a Few years and it was working fine til i got deplyed, had it in storage for 2 years and 8 month, just got back on July and decided to unbox it and use it but now i think i have a power problem with my 27" magnavox tv model 27MS343S. Once i plug the TV the standby light turns on, i press the power and it powers up, the screen comes on but when i press any keys (channel up or down, menu botton or anyother) the TV shuts off. i afterwards nothing responds i have to unplug the set to go back to the Stnadby light on. Any help would be greatly appreciated. SGT Leo