Edit needs far too much disk space

[hhatkin]

Here's the latest to spring out of DVDMF4 at me:
It has edited DVDs quite happily before but it has suddenly begun producing messages saying there is not enough disk space in the temporary work area.
This is to edit a normal DVD with only 2.5gB on it, and when the work area actually has 16gB of free disk space!
A complete uninstall and reinstall have made not a scrap of difference.
Any idea why DVDMF4 has suddenly become so greedy for space?!