Ok, so after spending some time on the probelm mentioned above (not the saving on macs problem) I've deduced that the fault seems to lie in the memory allocated to the program. This is annoying as I've altered the VM settings in NetBeans to allow up to 1gb of heap memory in the jar file but this doesn't seem to be the case, only in the IDE (to which I had also edited the startup file to do the same).
So any large template or background image loaded is blowing the allocated heap size and the program continues on its merry way without loading stuff. I have no idea how long it has been like this really. Has anyone who has used this to create forests in the past had a problem with larger templates?

Anyway, I've found a pseudo work around for now. By using a wrapper on the jar file I can create an exe and redefine the memory allocation of the program. The program I have used to wrap it is called Launch4j which is a free app that apparently can also create mac, linux and solaris executables. I'm new to this though and not sure if I can create a mac executable on the PC though just by giving it a different extension or whether it needs to be done on a mac.
So for now I think I'll just get it into a presentable state and then upload the jar file as usual so Paul can test the saving on the mac and if anyone has any comments on this memory problem I'm all ears.