I've just launched an instance from image CentOS-6.5-x64 in FI-Ware FiLab.
I've created and downloaded a KeyPar. When trying to connect for the first time - ssh -i - it is asking for root password.
Does the image have any default root password set?
I think that the problem that you have was answered in the previous link:
Accesing to a VM on Fi-lab
I hope that it is the problem that you have.