Held Open Shed II a week ago, and Berzerk was the only game to die

Today I had the chance to look at it... Got it to boot and play normally again, but the way I managed to get it to work puzzles me..
When every board is correct connected, it wont boot, not even a single "beep"...
I started to disconnect the boards one by one, and then apply power, and when i disconnected the speech pcbs output (not the flatcable) it booted, and went into attract, now it was playable, but with no speech (doh) I then connected the wires to the speakers again, and there where speech....

Powered down, and powered on, but no beeps....., then i disconnected the wires from the speech pcb again, and powered on, everything works!!!??
I have 3 spare pcbs for my berzerk, and tried interchange them, but with the same result - wont boot when the speech pcb is connected to the speaker...

Any input?? is it a shortage of voltage on power up??