What OS are you running? I know Windows can often be flaky about going into, and especially resuming, standby mode.
I've triple-checked the jumpers, but I can't get my carnetix 1900 to wake up or put my mac mini to sleep. The mac mini is configured properly -- when I press the power button manually, it will wake up and go to sleep. In fact, I've been running it in my car this way for the past few weeks.
On JP1, I've tried setting jumpers 3,4 and 5,6 which doesn't work as well as just 5,6, which also doesn't work. I've tried hooking it straight to my mac mini as well as just testing the continuity from the power button cable. Is there something else I'm missing or is my power supply messed up? It seems to work properly other than actually turning on and off the computer.