Based on the additional line of information in the duplicate report:
> The same problem also happens when I am using any help files.
possibly the same issue as Bug #649050 "Inkscape: All functions in Extention menu fail plus most in Help menu"
which itself is a duplicate of Bug #643272 "[win32] 0.48; extensions do not work"
Based on the additional line of information in the duplicate report:
> The same problem also happens when I am using any help files.
possibly the same issue as
Bug #649050 "Inkscape: All functions in Extention menu fail plus most in Help menu"
which itself is a duplicate of
Bug #643272 "[win32] 0.48; extensions do not work"