The problem is that your default file format in Excel is XLSX and a SaveAs with no given file format uses that. Please read the help to SaveAs in VBA for details on the file format argument.
So if you create a new file from this template you have a VBProject, which can not be saved in a XLSX file, hence the error.
If you want to suppress this error execute
Application.DisplayAlerts = False
before you save the file as XLSX
Otherwise use
ActiveWorkbook.SaveAs name, xlOpenXMLWorkbookMacroEnabled
BTW, "Name" also a VBA method, I recommend to use
Dim FName As String
instead.
Andreas.