What kind of cells did you use? Some CR123 lights will cook if you try and use 3.6-4.2V RCR123s. Thats user error though, not Inovas.
Did you insert the cells the right way? Some Inovas are designed backwards, you insert the cells with the + side towards the tail. Its counter-intuitive, but thats how they are.
Are you using fresh cells?... by that I mean KNOWN fresh cells... not the OEM ones that they ship with and everyone "tests" in the store.
Clean all battery contacts and threaded parts. I use a safe for plastics electronics part cleaner/solvent, the kind in an aerosol spray can.
Inova DOES make GREAT lights and are an upstanding company. You should be able to exchange it for a good one if you bought it from a reputable retailer. If its still under warranty, Inova will honor that too, give them a call and get the warranty repair process going.
One isolated incident is not reason enough to bag a company as a whole. Give them a chance, let their customer support do their job and make it right.
Ah, the cross examination.
Let me see, the batteries are Energizer 123 3v lithium, they came with the light. They came with the + ends towards the tail cap switch as do all Inovas I have.
They were fresh enough to burn the light out, isn't that fresh enough? My light came sealed in it's packaging from Bright Guy, it wasn't a display model.
There is no need to clean anything, the light is entirely new and shiny.
I am an Inova fan but these forums are for us to help each other, if Inova needs to check their manufacturing process then I hope this forum helps and otherwise we can at least warn each other.
I have the following Inova flashlights:
X5 - Perfect.
XO - Reflector has some roughness, otherwise perfect.
Bolt AA - Reflector has some discolorations, otherwise perfect.
T2 (2007 with reflector) - Perfect.
Considering that I am just one customer and have seen what I have seen in my own purchases, I believe Inova should check it's manufacturing process.