I'm currently running BackTrack 5 R1 with proxychains, tor and privoxy configured. However, when running a scan with nmap through proxychains, the target machine shows all ports as closed. When I run the same nmap scan without proxychains, the target machine shows open ports.

Is there something I don't have configured correctly? When I browse the web tor works without any issues.

Below are the scans I ran. (x's being the IP address of target machine)

Code:
proxychains  nmap -sTV -PN -n -p21,22,25,80,139,445 xx.xx.xx.xx
Code:
proxychains  nmap -sTV -PN -n  xx.xx.xx.xx