The actual solution is that you have to make two edits to the PS field to get it to save the change. It's a glitch in the 1.5.2 version of Precious Stones that doesn't get fixed till 1.6.2. So, when you want to add someone, do
/ps allow ChiefCrazyCowThen perform another command on the same stone, like:
/ps allow notchIt will allow Notch into your field but he probably won't log in and find his way to your field

Some people add Plenary to their fields for good luck, lol.