I am also having this issue, I have gone through your tutorial a multitude of times and gone through a couple others. The modpack.jar is a jar file and they are in the correct folder. Zipped together and uploaded to dropbox under the public folder I coppied the link and put it in my mod pack on the Technic site. When I launch it in the launcher it downloads it all but when it runs it is not modded. I know it has to do something with the jar / bin because when I look in the modpack folder the technic launcher makes everything else is there.
http://dl.dropbox.com/u/36325003/Frostcastpack.zip