I'm using Calibre v 0.8.3 and LibreOffice 3.3.2 in Ubuntu Linux. I am able to add an .odt file into Calibre and convert to epub. I also tried saving the LibreOffice document as an Aportis pdb and inputting that into Calibre and then converting, but that did not look as good as the .odt to .epub conversion.
I'm trying this with rather simple documents that have no headers; so I'm not sure how the TOC would come out. I have found pdf to epub conversion to be the most problematic; so I would suggest you take pdf out of the equation where possible. In this case, odt should work, but it may not work in the earlier versions of Calibre. You might want to try save as .doc, because I am pretty sure earlier versions of Calibre converted .doc. Or best of all, you can get the latest version of Calibre for Linux or Windows at: