Bluetooth-question: why are certain devices never shown as paired?

I have a second Windows computer (a tablet PC). When I set up a
bluetooth connection between the two, I have to enter the same key on
both ends and the BT SW tell me, that the two are now "securely
connected". But why is that (and only that) device not marked with a red
checkmark (as is normally the case with paired devices)?

And - probably due to the same reason - I always have to go through this
connection procedure again each time I want to connect. Why does XP not
memorize that device as paired and well-known (as it does with others -
e.g. my headphone and my PDA)?

Michael