looks like the memory on your gfx card is shot i had similar problems i bought a new gfx card and it played up sometimes in windows and more so in daoc.
run a benchmarker on your gfx card and compare the results with others with the same card.
Benchmark your card using 3d Mark 2001 and watch for graphics artifacts in that.
Also download Rivatuner from http://www.guru3d.com/rivatuner/ and lower the clock speed of your graphics card core and memory. The FX5600 usually has a default core speed of 325Mhz and memory speed of 550Mhz, it could be that yours has jumped beyond that due to some driver corruption/issue. I'd suggest lowering to 300Mhz and 500Mhz. If after that you still have artifacts then dump the card