I think if there are antenna's (a.k.a. long wires) hooked up to the option pins, the internal pull-ups may not be good enough. Small jumpers or dip switches should be ok though. No problem adding external pull-ups if desired. Or you can tie them directly to VDD or VSS.

With the IdleState pin left open, the program will assume the input idles HIGH, with negative going pulses, which is the opposite of the 0-12-0 polaraity described before. So I'd start with that pin grounded.

The Invert input should be left open, without any wires, since that circuit uses the NPN transistor that inverts the output. It was just an option available for anyone else that might pick up the code from the forum. The output follows the same polarity as the input Idlestate, so there shouldn't be a need to change it with that circuit.

When you programmed the chip, did you uncomment the ANSEL line?
I was using a 12F629, but I think you're using a 675.
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