The HTML Help 1.x compiler is not Unicode compatible and can fail when compiling a CHM that contains non-latin or special (e.g. $,!,*,& etc) characters in the path name (i.e. the full directory name and / or the file name).
The solution to these compiler failures would be to change the output filename so that it only includes latin characters. You can change your CHM's output filename by opening your Build Profile for editing, select the Format page menu item then edit the Compile help file to field.
The HTML Help 1.x compiler will also display warnings / errors if the output path contains ".h". This issue will occur if you have Other Files or Topics that contains ".h" in the name, the solution to this issue is to ensure that your output path, Other File's names and Topic names do not contain ".h".