O problema com a tecla Num Lock no Remmina pode ser corrigido com a instalação de uma versão mais recente do ppa: remmina-ppa-team / remmina-next . Isto é o que eu tenho no Linux Mint 17.1 (baseado no Ubuntu 14.04 LTS):
$ sudo apt-add-repository ppa:remmina-ppa-team/remmina-next
$ sudo apt-get update
$ sudo apt-get upgrade
$ dpkg -l | grep freerdp
ii freerdp-x11 1.2.0~git20141201+dfsg1-0trusty1 amd64 RDP client for Windows Terminal Services
ii libfreerdp-plugins-standard:amd64 1.2.0~git20141201+dfsg1-0trusty1 amd64 RDP client for Windows Terminal Services (plugins)
ii libfreerdp1:amd64 1.2.0~git20141201+dfsg1-0trusty1 amd64 RDP client for Windows Terminal Services (library)
ii libpam-freerdp 1.0.1+13.10.20130724-0ubuntu1 amd64 PAM Module to auth against an RDP server using FreeRDP
$ dpkg -l | grep remmina
ii remmina 1.1.1-1+547+next~ubuntu14.04.1 amd64 remote desktop client for GNOME desktop environment
ii remmina-common 1.1.1-1+547+next~ubuntu14.04.1 all common files for remmina remote desktop client
ii remmina-plugin-rdp 1.1.1-1+547+next~ubuntu14.04.1 amd64 RDP plugin for remmina remote desktop client
Parece que esta compilação do remmina usa o freerdp-x11.