I just ant to confirm that the Patriot 4GB stick (http://www.amazon.com/gp/product/B004CVSV2W) works fine in the ReadyNAS Ultra 4 Plus as well. I have run it for one week now and it works fine. There were no errors while running the memtest.
Model: ReadyNAS Ultra 4 Plus [X-RAID2]
Firmware: RAIDiator 4.2.17
Memory: 4096 MB [DDR2]
Hmm, I just installed this memory in my Ultra 4 Plus and it shows: "Memory: 1024 MB [2.5-3-3-7]" I was planning on running the memtest but just plugged it in and it booted, so I checked the status page. Any ideas?