I use windows 7 system,

heck and open the following file with notepad :
C:\WINDOWS\system32\drivers\etc\hosts

Make sure this file does NOT have any line containing master.liveforspeed.net.
If it does, remove that line.
Then restart your computer and try to connect to the master server again.

I have already buy the S2 licence, but in the game , after *I type the
correct user name and password, I click " unlock" , it show " waiting for
reply from master server" , then after a while , it show " no reply from
master server . *I have tried to turn my firewall and antivirus software off
on my computer, but it doesn't help. anybody know? i wlil appreciate it