>Both fs_frmmaintenance and fs_Header are classes in the same classlib (vcx) file.
>fs_frmMaintenance errors and fs_Header1 not and is created.
>NewObject, to my opion requires newobject(cObjectName, cClassname) and not the cClassLibraryName, VFP will look in the loaded classlibraries (VCX) files for the Class = 2ndParameter.

You're right, the classlibrary parameter is optional, and the help claims it defaults to .vcx - thought I could swear I saw it find a .prg in a project (or on the set("path") perhaps) and not a .vcx when extension was omitted, but then my memory isn't as I remember it.

So we're back at square one. In cases like this, I'd just go to class browser and copy-paste the name of the class from it into the code, because my eyes also fail me sometimes and the obvious typo isn't.