One other thing to try is to use Direct3D mode. We have found that the 9x.xx series of nVidia drivers and OpenGL in Ryzom do not like each other that much.
Go to
http://www.memtest.org and download a copy of memtest to make sure that your RAM is not starting to fail.
A power supply that is starting to fail is usually the last thing diagnosed as the errors always look like other bits of hardware are failing. Ryzom may be forcing the video hardware to push the PSU just over the edge.