I received my USBtinyISP kit today (127619) and built it this evening.
The green LED does not and has never lit up. I would appreciate any suggestions you may have.
I have verified that the LEDs, zener diodes, ICs and the electrolytic capacitor are oriented correctly, verified that the correct resistors are in place, tried three USB cables, tried all five USB ports on the computer, reseated the ATtiny2313 MCU, and re-heated all solder joints.
I measured 5 volts from the USB port on the power pins of the ICs and headers, and the oscillator waveform is showing up on pins 4 and 5 of the MCU. Pins 1 and 20 are HI and all other MCU pins are LO. The 74AHC125 has pin 14 HI and all other pins LO.
My computer is a 2.0 GHz Intel Core2 Quad Lenovo Thinkpad W700 running Windows Vista Business 64 bit with 6 GB of RAM.
I haven't gotten past plugging the USB cable in and looking for the green LED to light so the programming software, chip, screenshots don't seem useful at this time.
The front and back pictures of my USBtinyISP are below:

