Problem with ineptpdf: "Error: FOPN_fLock not supported, yet ..."

Re: Remove DRM from PDF ebooks (Adobe Digital Editions)

 

I have installed "Adobe Digital Editions" and used ineptkey.pyw to get the "adeptkey.der" and it worked to obtain the key.
Now when i open the "inept.pyw" it automatically select the "adeptkey.der" file, i specify the pdf input file and the pdf output file too and i get an error:

using ineptpdf7.4.pyw the error is :
"Error: Unknown filter: param={'Filter':/FOPN#5ffLock, 'V': 1}

using ineptpdf8.4.48 the error is:
"Error: FOPN_fLock not supported, yet ..."

any suggestions?