RN 3200 and AD

I don't have that kind of configuration. I suppose you already tried to find the user in the web interface with no success and that you tried to make him log to see if it appeared after ?

Yes I searched for the user with no luck, it doesn't show other domain's users and I can't see anything with that user. I have that admin account connected to a SharePoint farm search and my final goal is to show NAS results in the site.

This is indeed a problem... I don't remember that much about share point but I think you can only have one account for search. It isn't possible to create another account on the NAS domain and use it, am I right ?
I would advise asking support from Netgear directly, it can't hurt opening a case (some admins wander around too, so you can edit the title to give them the case number, so they can cross reference things). I don't think many people have an infrastructure like yours where they could do tests. I have an enterprise-like network at home and even then I'm far from having a full sharepoint farm and AD trusts. Best I can do is single sharepoint + single AD, my ESX server with 16Gb ram will let me down after that, not to mention non-raid HDD... Netgear however may have the ability to do some tests and have a better knowledge of the implementation of AD authentication.

Thanks a lot for your response man. Ye I will try contacting them to see what I can find out. Our environment is very nice for development and tests like these and I want to make the most out of it, that is why I want to figure out how to accomplish something like that :)

I think I'm already privileged to have genuine licenses for MSDNAA, office, VMWare products for free I also picked a Cisco 1812 for 20€ and GS108T for 10€ that handle Vlans and applicative firewalling. With all that I can compete with most enterprise environnements but I'm limited by my hardware (i7-2600k, 16Gb RAM, 2*750Gb caviar black that ESX won't let me mount in raid) and my internet connection (100Mbit/s down, 5 up). When you know the prerequisites for Sharepoint and Exchange you get scared... And when you'd like to put some oracle products in it along with a decent UTM with IPS you quickly find the hardware limit. That said I can still get some fun out of it and a 32Gb upgrade is possible for my motherboard...
But what you have is truly amazing if you have the control of it, you just have to make sure you don't mess things.

Do not hesitate to keep us posted, I am interested by the way you bypass the problem and maybe with some more elements from Netgear I will be able to help more.