I maybe missing something obvious here but as a new Calibre user I added a RTF source file, converted it to EPUB, chose the "Save to disk | Only EPUB" and when I try to open this epub inside Mozilla (EPUB Reader plugin) the TOC and cover displays fine but any link from the TOC goes to a broken link page like this:
Firefox could not find file: /C:/Users/coleccionista/AppData/Roaming/Mozilla/Firefox/Profiles/lgeeg00l.default/epub/244/"_Toc192588919
Using the "Advance" button to browse chapters seems to work OK so I don't know if this is a problem with the links used in the TOC or a EPUB Reader issue
Viewing the book in Calibre works fine.
btw, the conversion from RTF to ePUB appears to be pretty good
PS: Opening the file in SIGIL and going straight to "Save" seems to fix the issue, there must be some kind of problem with the links generated in the toc.ncx file