Different results for different parallel ports, same circuit. why?
I'm not entirely sure, but i think i've come across a similar situation once: The status byte of the parallel port always reading the same even after changing electrical inputs at the port. What i did then was to select, in the PC's BIOS setup, an option for the parallel port OTHER than 'standard'; i believe i chose ECP. After that (and no other change), it started working and reporting values as expected. Since you say you explicitly selected the standard mode for the port, you may want to try that.