My PC freezes just after selecting MULTIPLAYER from Resistance's main menu.

While many things may cause OFP to freeze your PC (search The FAQ for "freeze"), OFP reg Stephen Morton, a.k.a. Medwaypvb, says his freezes were caused by his firewall software having rules that were only appropriate for Gamespy when playing OFP's older version. By deleting the old OFP/Gamespy  permission rules in his firewall and  then restarting OFP: Resistance, new firewall rules were created and Stephen has since been playing happily ever after!