Yeah, I was building a USB power injector, so I could make of USB host mode. I had a nice circuit working on breadboard with a 9v battery and a 7805. Unfortunately, when I decided to put it on a little piece of veroboard to make it more permanent, I connected the battery to the output pin of the 7805 rather than the input pin... And of course I didn't check it before I plugged it in...

I admit I'm an idiot to do it, but it's done, and someone may as well benefit from the remaining parts :-)