STK300 compatibility with AVR-PG2 Parallel Port ISP?

I just got (2) AVR-PG2 Olimex brand Parallel Port AVR ISP programmers that I ordered. They work great with a Kanda STK200, and with an Olimex AVR-H128B. They do not work with a Kanda STK300. (Obviously, the Kanda STK300 is defective, right?)

I tried the Kanda STK300 with a Kanda STK dongle, and it works just fine. The STK300 stops working when I plug in the Olimex AVR-PGs, and starts working again when I plug back in the Kanda STK dongle. (Obviously, the Olimex AVR-PG2 is defective, right?)

It’s not plugged in backwards - the connectors are keyed, and I checked the orientation vs. other dongles and boards to be sure.

Any ideas? (Thanks in advance)

Andy Out!