Hi Hood,
Thanks for the reply, it is very much appreciated.
I have checked the screenset, as suggested, and can confirm that the hotkey is enabled for the reset button.
I have concluded that it may not be a screenset related problem as I have two computers running Mach, my internet computer (the one I am using here) and my workshop computer. The same screenset works as expected on this computer but no longer responds to the @ key on my workshop one. I have also checked for different ascii values for the @ key on the different keyboards but the mystery of why it used to work but doesn't any longer still defeats me.
Any further suggestions would be well received.
Tweakie.