I am trying to get passive FTP setup but am not having luck.

I have added the following to the proftpd config file:
PassivePorts 49152 65534

Doe it matter where exactly I put the above directive?

I am behind a nat so I opened up the ports 49152-65534.

Is there anything else I am to do? It does not work. Using PORT works fine.

Your NAT device also needs to know about passive FTP. If it's Linux, that'd be the ip_conntrack_ftp kernel module.

modprobe ip_conntrack
modprobe ip_conntrack_ftp

I am actually just behind a NAT router and have set up port forwarding there. Linux firewall is turned off.

Howdy,

The FTP server itself may need those two ip_conntrack modules Joe mentioned loaded as well.

If you run those two modprobe commands on it ("modprobe ip_conntrack" and "modprobe ip_conntrack_ftp"), does that help?
-Eric

I am actually just behind a NAT router and have set up port forwarding there. Linux firewall is turned off.

Are you sure that device supports passive FTP through its NAT? Not all routers do.