Hi Mugelpower,
Here is what I think, <b>I say think because I do not definately know.</b> Being that your config fuse setting is WRONG, I think your PIC is not properly set up for EXT OSC and that is why it will not accept input on RA7, I THINK it it using the oscillator as a crystal, somehow getting enough signal to work, elsewise it may be defaulting to int osc, who can say? Try sending out some serial data to a serial lcd and see if it scrambles the data, better yet correct your config statement and then try the OSC on it's proper pin. I compiled your code both ways and the hex files have some distinct differences. One more thought, the PIC is probably using the default config statement in the 16F628A.inc file, unless you have commented it out.