My problem has been resolved by having a triple boot machine. Fedora 17 32 bit with gretl 1.9.11 does not crash.
All with the same gdt file.
gretl with windows 7 professional - ok
gretl with ubuntu 1404 - not ok
gretl with fedora 17 - ok
I went with Fedora 17 as it appeared to be the latest version at 32 bit. I think the gretl version I used on Ubuntu was 1.9.14 - I am currently on the Fedora disk. That means that I cannot be sure that the problem rests with Ubuntu or the version of gretl that I was using. The comments I had back were sufficient to cause me to triple boot my netbook and step around the problem, so thank you.
Finally, the reason I was keen to use gretl (rather than my expensive Minitab licence) is simply the output of the model - OLS option is better / more compact and more readable than Minitab ( in my opinon). So once again thanks for that.
The next part of my current project involves applying data to a Weibull distribution. I have been using Minitab for this for the last 15 years but I am happy to move if something better is available - any ideas?