My short experience with coiled-coil is that molecular replacement can be difficult for "classical software" (due to the very anysotropic shape of the protein). In our case (a short parallel dimeric coiled-coil), molecular replacement trials using AMoRe or MOLREP were unsuccessful. We solved the structure using EPMR (evolutionary search molecular replacement software). http://www.msg.ucsf.edu/local/programs/epmr/epmr.html
Michel.
