Ok man, I'm just trying to help, but it's difficult not being there. This should not be a complicated problem. Maybe Raenon was right and your regulator is just screwed up. In my thinking, if you're sending out 25psi through the regulator, you should be getting roughly 12.5 through both lines, and that should be fine. What's so weird is that you said when you hooked up just one you got NOTHING?!?! How did you hook the one up? Did you just pull the other line off, or bypass the splitter entirely? If you just pulled off the one line, the CO2 obviously just leaked out the unhooked line. Is this a set-up that worked fine with one keg, and the problems occurred once you went to two?
I want to help you so bad because I'll be doing the same thing soon, I just can't imagine so many problems with such a simple setup! Unhook the splitter, and just go straight to one keg. If that doesn't work you've got some other kind of problem. Bad regulator, leak, etc. We'll get this thing figured out, it's just difficult over the internet. If I was there, I'd have things fixed in no time! A way to check your regulator is to turn off the tank, wait an hour, and see if the pressure held on the regulator gauge. If it doesn't, then the problem is obviously a leak.