Best unix OS for IPTV solution

hi,

I am asking about light Unix based OS that will be installed on small PCs (vesa pc) these PCs will be mounted on the back of HTV or LCDs, hotel guest will be allowed to use Firefox Mozilla browser to enter our web based IPTV system (Flash, Java, Javascript) and also surf internet. VLC or Mplayer is used with their Mozilla plug ins.

no other service is allowed and system must be totally blocked for other applications or actions, we are currently using STBs for this purpose but we want to provide better service without going high with price, so we must keep the pc to be limited one.

sorry for the long information. can you please advice me with the best OS to be installed at the client side. other ideas will be also helpfull.

Thanks for your help and time.

Regards