I guess we will need some more details about this to be able to answer your question.
First of all I would advice you to check the URL list in JoomSEF and search for the URLs in question -- that is \"..../from.html\" and \".../from-2.html\". (use filters to find them)
After you get them, check what is the original non SEF URL and how do they differ. That should give you answer. If you are not sure about it, post these non SEF queries here please.
Also please, check your JoomSEF configuration based on our
FAQs that are discussing duplicate URLs /