I am having problems myself downloading. I made my own modpack, put the zip file on dropbox, and connected it to the modpack. I tried installing it, but everytime I try to, the zip file goes down by a million percent (-134913641%), and after 4 seconds, either says: "failed to download", "failed to unzip", or "zip file not found".
I think it is an issue with the zip file, because there are no clear instructions on how to properly zip a file. It is running on 1.5.2, and the zip file contains 4 folders:
1. Bin Folder, with nothing in it (they said I need to put modpack.jar in it, but I don't know how to do that very well, and I have no mods that require being placed in minecraft.jar)
2. Mods folder, with all mods. Mods were tested on a forge client for 1.5.2, and they all worked.
3. Coremods folder, with all coremods in it. Tested, it is working
4. Config, all config files are in it.
Am I missing something? I probably need forge, or does it automatically install? I think the problem is not with downloading the file, but the file missing important data.