Um..I'm a total newbie, but, if you only have one section, will you even get a Sections dialog? Can you put everything in one section? Because mine goes start, license, directory, installing, done.. No section page at all..
I fyou put a - for the name of the section then the commands in that section will always be done. So, if the name was install then the section should be called -install,
or you can leave the sectionname clear, it has te same result.
Before thinking of anything else: Download latest version of NSIS. This will in most cases solve the problem. Some part of the script may be changed to fit the new version of MAKENSIS, but it's worth it. http://www.nullsoft.com is the place!