Josm move visible area

I have been running Josm on two Mac machines for some time and on both, an IMAC and a MAC Book Pro, I have use the shortcut Ctrl + arrow to move the map around. On both machines I have installed Lion OSX 10.7 and the latest version of Josm tested 4279. But now I am unable to use the shortcut on the MAC Book Pro, but it still works fine on the iMac ! I have done a search for a problem and I have found a chart showing the shortcuts on the WIKI .This shows the shortcuts that I used to use as “Move visible area”. Looking at the Josm shortcut preferences on both machines I can not find any shortcuts that use the Ctrl as the first key.
My big problem is that I am not too sure that the “Move visible area” shortcut is defined in the preferences of Josm as the iMac does not have them there, but still acts correctly on the shortcut combination. Can anyone point me in the correct direction as to where these shortcuts are defined, and how to add the ones that I would like.