Many thanks for the reply. I will try this and report back.
Before I do so I have tried one more thing, which was as follows. I have another PC - running the same version of Mach 3 and on Windows XP OS.
Used this PC to drive the CNC and it behaved normally - i.e. the FRO is not locked down to 2%.
My thinking was - how can I compare the settings on the XP laptop / Mach 3 (which works) with the settings on the Win7 laptop (which has the problem)? - it may be that this could identify some differences that might explain the issue.
With regards to the xml file that defines my profile. In my c:Mach3 folder I have a text document called profile.txt. When I open this the content says "Mach3Mill". It this same folder there are 3 files that have an xml extension. One is called - Mach3Mill.xml - is this my profile or xml file that I see referred to in various posts? (sorry if this is a really basic question).
Andrew