Readynas Duo crashes (or hangs) on big filecopy

Then I explained myself poorly. At first the problem appeared when I copied files from one place on the nas to another place on the Nas. I did this with Nautilus (file manager) on Ubuntu with cut and paste. Because the file goes then to and from the PC it generates heavy network traffic. I then got the idea to do the same copy on the command line of the Nas (thereby eliminating network traffic, also much faster ofcourse). I got the same error then (hang/crash). Then I did the copy while in another shell examining the tail of the messsages file. Then it was clear that the error message (rxS ...) coincides with the hanging/crashing. As the power down button works I think the system is still running but network connection failed. (I don't see a connection there except both involve the kernel ofcourse)

My filesystems are not full (by far)

I think of running a script that logs the processes so that I can see something when the system hangs (or network traffic is down)

I will swap the PSU with another netgear PSU and see what happens.

I will try to find the disk tool.

Thanks very much..