As the bookmark is from a form field, the error relates to the fact that the field construction is toggled. It would be preferable to leave the field locked and use
Code:
ActiveDocument.SaveAs FileName:=ActiveDocument.FormFields("ActName").Result
Personally I would give thought to changing the form fields to content controls as processing such a form is much faster with content controls, especially in Word 2010. You can convert them with
http://www.gmayor.com/ExtractDataFromForms.htm