Mori Seiki CV500-B + MSC-803 PC File Tranfer via RS232

Hello, I'm struggling with this problem for a long time, and I hope I can't find some help here from you guys.
Let me start by saying that I'm a total noob in this matter, but with good guidance I can get where it's needed.

Here's the deal, the company I work for as an 1998 Mori Seiki CV500-B with an MSC-803 NC Unit.
I've been working just fine with it, but only using macros. We would like to leave the macros alone and start using transfer files with GCODE (*.nc files ?) to the machine in order to simplify the whole process.

And this is where the problem begins!

I'm using a NULL MODEM cable.
I've followed some transfer procedures from the user manual, but couldn't make it work.
This machine was used and came with the computer that was connected to it in it's previous company, so I'm using CIMCO Edit v5 (which was already installed) to edit and transfer files.

I've checked the GOP parameters for RS232 an they are all according to the manual and are the same in the PC.
Not sure which RS232 port to use (NC or GOP).
When I use the NC RS232 port nothing happens, can't read, can't write.
When I use the GOP RS232 port I can receive files on the PC but they don't come in code, just gibberish numbers and symbols and when transfering from the PC to the CNC the NC unit spits out an "OVER MEMORY" error, but it has plenty of space left.

If someone needs more info I can provide it to you, I'm just so frustated with this right now that I can't even think properly.

Would really appreciate some insight and help with this matter, thanks in advance to all.