i found a different solution. in my case one of the files called: fml_libs15 . was corrupted so all that i did was simply delete it. and after that my launcher started working again.
to get to the file...
1. lick on any mod-packs "settings" icon
2. go back to the folder .techinc
3. open the folder called cache
4. delete the folder named fml_libs15
after that, the launcher should download the folder again and work this time.
i did this because it was the only zipped folder i could find and the launcher said it cant open a zipped folder.
so it was pure common logic.