what version of Dreamweaver? What version of extension manager?
1) Uninstall all versions of UE and DFP
2) Download the new UE4
3) Open up DW cs3 or cs4
4) go to Commands->manage extensions
5) click the install button and browse to the ue4 .mxp file
let me know if this works, if not let me know the dw and extension manager version you are using.