Sorry for the necro bump but I thought I would leave this here to help anyone who has this issue in future. I have just had this problem in Firestorm after recieving a new router from my ISP. I solved it for myself without uninstalling or going through a long process.
1. Close all processes of Firestorm
2. Browse to C:\Users\YOURUSERNAME\AppData\Roaming\Firestorm_x64\user_settings\
3. Delete bin_conf.dat (click yes for admin rights)
4. Reopen Firestorm.
Hopefully you should now be able to login as normal. I hope this helps you.