this is currently my set-up:
a TP-link TD-W8910G aDSL router which connects to the internet,
- my home PC and
- an Iomega ix2-200 NAS device
hardwired to the router.

I try to set-up remote access and personal cloud for the Iomega NAS.

I get the next error message:
either UPNP is disabled (which it isn't, I tried both) or I have a problem with port mapping (which is the more likely cause).
Your network router could not be configured to enable or disable remote access. This can occur when your router does not have UPnP enabled or the required port cannot be opened or closed.

I tried googling but didn't find anything specific enough to help me out.
I need the port ranges and protocols (TCP ?)

I tried some settings I found on the web but they didn't work.
Could someone please help me out here, or point me towards a pdf or link where this is explained in detail?

On the router, under the NAT tab, I've got both virtual servers and port triggering options.
I tried adding, under virtual servers, the ports 20-21; 80; 443; 6881-6999 as per this link, but it gave an error message about port 80 already being in use.

also, what should I set under "server IP address" when setting these virtual servers?

any help much appreciated...
I'm not very computerminded when it comes to setting up these kinds of things...