Custom ROMs can break functionality built into the dialer for activation. I had the same problem trying to activate my HTC Droid Incredible with Metro, everything was in order but the phone would not work. I had to flash to a complete stock ROM, then when I called Metro for the 4th time, as soon as I got off the phone to put the HTC on my account, a bunch of activation notices popped up, then the phone rebooted, and suddenly, SERVICE!
Take a chance if you want, but you should flash back to stock to avoid problems. Oh, and you CAN activate while running PlayfulMod, proven by my mother in law taking my old Ascend with PM on it, and getting her own service started.