There appears to be another RADIUS server runningon the authentication port 1812

[Thibault Le Meur]

># netstat -tunelup Aktive 
> Internetverbindungen (Nur Server) Proto Recv-Q Send-Q Local 
> Address               Foreign Address             
> State       Benutzer   Inode      PID/Program name   
> [...]
> udp        0      0 192.168.100.207:1812        0.0.0.0:*     
>                           
> 0          7223       2012/mp_kerneld.x   
> udp        0      0 192.168.100.207:1813        0.0.0.0:*     
>                           
> 0          7224       2012/mp_kerneld.x   
> udp        0      0 192.168.100.207:1814        0.0.0.0:*     
>                           
> 0          7225       2012/mp_kerneld.x   
> [...]
> 
> There you are. Some program named mp_kerneld.x is occupying 
> the port. That's 
> why freeradius won't start.

See this Thread:
http://www.mail-archive.com/freeradius-users@lists.freeradius.org/msg33532.h
tml

HTH,
Thibault