When trying to create a new document from a template (File - New - Templates and documents), the error message shown in the summary appears.
Same problem here.
I have the same problem after removed 3.4.5 installed 3.5
I removed Libreoffice, deleted the User folder under Home>.config>libreoffice>3. Reinstalled Libreoffice. The problem is gone. However some customisations (like custom toolbar) is also gone of course.
I strongly suspect several recent (3.5 or so) errors are tied to the aging openoffice templets & extensions. For those who don't use such things it's an easy fix; but for those of us who use many templates or rely on old extensions, this is a problem.
*** This bug has been marked as a duplicate of bug 46155 ***