I'm only jumping in here to ask Grumpy_Mike about
Does that include the 1uF capacitor on the latch line? That is a big mistake and can damage your arduino, they refuse to correct it. Instead wire it to the 5V on the shift register chip, keep the other end at ground.
Please see my Nick Gammon's post and my questions at: 4-digit display made from minimal parts - #14 by system - LEDs and Multiplexing - Arduino Forum
It's a clock based on Gammon's example, and I DID add that cap on the latch line as mentioned in the shiftOut tutorial, however I do NOT have that cap from shift register pin 16 Vcc to Gnd as Gammon shows. The project has been working fine for some time - should I pull that cap off the pin 12 (latch) line???
Thanks you!