Hi, stevtar,
It sounds like one of the HTML Help viewer components,
itircl.dll, is missing or incorrectly registered on this one
machine. You should be able to resolve the problem by running MJ's
Help Diagnostics, which is available from here:
http://helpware.net/downloads/index.htm#MJs
If you continue to have problems, can you paste the "HTML
Help Run-time Components" section of your MJ's Help Report into a
reply?
Pete