i bought a new flashlight that has Three LED Diodes in it,when i bought it was working fine,and bright....after two Days use one of the LED's burns alot dimmer than the rest and Flickers..the two other diodes are normal brightness....but one of those Flickers too,what is happening?!

I would hazard that the LED chips are being seriously overdriven. Most likely they are connected directly across the battery, with no current limiting resistor, and the batteries are either Alkaline or lithium cells, with a low internal resistance. One of the chips had a slightly lower forward drop, and drew higher current, and got hot and (due to negative coefficient of voltage drop with temperature) eventually broke the bonding wire, The die then cooled and reconnected the bond wire, creating the flickering. The overheated chips then lose efficiency and dim out.

I have the same problem with cheap lights, and have added a current limiting resistor, somewhat difficult in the confined space inside.

Other alternative is to use older cells to run it in the interim, but nothing can be done for the damaged chips.

thanks Monkeyface!...the LED"s have no current limiting resistor in them and use alkaline's as a power source...the flickering is quite severe now.