Thanks guys
I have now tested with Decimal Feet, Engineering Feet and Architectural Feet.
All of the 3 models that are feet create an error.
All the rest of the models work.
This holds true for SU 7, SU 8 and 2013 for Windows.
The error is a bit misleading as it appears as a script error on line 1 char 416
The interesting part is that the html script doesn't have that many characters on line 1
This may be where I pass in a big string, and need to parse it. If that is the case then the defaults.txt file has a value that does not translate over to feet.