What, it wouldn't keep the 7 digit PIN, or the 5 digit, or the 3 digit? Which one? I don't think that the number of PINs that you've entered has anything to do with the problem, so it must be something to do with the PINs themselves. Are you prefixing these with zeroes? Could you include more information about a specific number/numbers that have not worked?

You shouldn't lose the PIN numbers if you go back into emplode. If you don't press the sync button, then you definitely won't.

Also, just to confirm: this occurs when you press OK, and then immediately go back to the dialog box, yes? Rather than having to go through a sync?