ReadyNAS NV RAIDiator 4.1.6: Alloc null skbuff in pool

It might not be anything to do with the memory if you added it a long time ago (though memory can and does fail sometimes so it'd be a good idea to run the memory test a few times). More recently RAM manufacturers having been messing with these modules under the hood rendering them incompatible e.g. changes in production of the Kingston module have rendered newer versions with the same module number incompatible.

You could have a hardware problem with one of your devices or cabling. Do you see any errors in the error count under Network > Interfaces?

I can find one thread with a possibly similar error (though it's quite old, don't revive it, keep your posts in this thread): http://www.readynas.com/forum/viewtopic.php?f=7&t=5780&start=0

I guess it may be possible that one of your devices doesn't support jumbo frames. Have you checked to make sure the NIC in your PC supports jumbo frames and that your router/switch does? If you disable jumbo frames do you still get the issue?

Also make sure you are using good Cat5e cables or newer.

You really want to eliminate a hardware problem before going and messing with configuration files (it's also a good idea to backup the configuration file before making a change in case you mess things up and don't remember what the old settings were).