Hi,
I've always had trouble using the VCC and ground symbols to run sims... I hooked it up with a DC source battery symbol and it works fine... maybe someone hear can tell us how to get it to work with VCC and Ground. BTW, you will need to connect pin 3,4,5 of U1 to 5V, and also connect some sort of clock to pin 14 of U2... Here's how I got it to work... Hope it helps.
Alex