All of a sudden I had the same problem yesterday - while my mate didn't. Turned out my "modpacks.xml" file was somewhat messed up, at least there were no "modpacks" listed at all. Replacing the modpacks.xml file (with the one I got from my mate) fixed the problem for me ... so you might wanna try that as well.
Attachment: zipped modpacks.xml file (clean, no viruses included, sorry for that). Extract to ... C:\Users\YourName\AppData\Roaming\ftblauncher\Modpacks ... or wherever yours might be located.