Netgear WPN824 and FTP (NAS)

Well hello there everyone, been away for quite a while, but now i have a very annoying one for all of yous :major

here's the description as detailed as can be:

- We have a NAS (black box that has a couple of hard disks in it, a network port, usb port, and runs by a firmware).

- We have a Netgear WPN 824 with an attitude problem.

now the NAS is connected to the internal network, (192.168.x.y) , and the FTP service on it is running, you can access via any windows explorer or any ftp software and do all the things you need to .

I have just made on the Netgear a "port forwarder" (not NAT option, it has been replaced by this i guess), for ports 20 and 21 to be directed to the NAS' IP address. ....

Now before taking for a long ride explaining the troubleshoots of several hours, here are the latest findings:

I can telnet the NAS using port 21 (using the external real ip), meaning the ISP didnt block it , but when i try to open it via browser or smthn else... it doesnt open at all , and gives the errors 227 and 200 going to passive and stuff like that.

I removed the passive option for ftp in IE, it started giving the 500 error , i guess that wasnt to smart.

On the other hand, i made another port forwarding rule of port 80 to the NAS as well (it has a web management thing) , and it would open from the outside world....

so am stuck here sort of... telnet is working, but not the full FTP , i tried even to open ALL ports , from 1 to 6344 tcp/udp (just in case the NAS switches ports for data, it didnt work as well).

This is really annoying, i was trying to help out at first, now its just a matter of challenge and me being stubborn to have it done.

Thanks for all the help in advance

Cheers
WK