what do you mean by "providers default"?
What do you have it set for when you lock it?
Have you ever been back to the Network Preferences after you have locked it but before you shut down for the night?
My Mac OSX 10.5 is connected to the Net wirelessly via an Apple Airport Express, with the Network Preferences lock ON.
But after restarting after overnight shut down, the Lock Is OPEN and the network has reverted to the provider's default, in this case "Fon Zon Free Internet" (not free!)
How is the lock being unlocked ??