I have finally given up and have downloaded MacDive...
Although it sounds like something form McDonalds, its a great software for Mac! Can highly recommend if as an alternative to the DM4 if anyone has the same ongoing troubles I have had for the last 6months. Its costs $30 and is very easy to set up/import existing dives
Finally my log book is up to date and I can spend weeks and weeks plotting my GPS numbers for dive sites :oD