I also experienced graphical errors and crashes after I used my system for some time. I tried my ACA1230/28 on a fixed 2b and 1.d4 motherboard.
I did read the installation manual, and had already tried to move the card back half a millimeter. But it didn't help.
I was really getting desperate, so I decided to move the card back a little more, up to a point where I asked myself if it wasn't too much. But to my surprise it worked this time.
I played some shoutcast radio for more than 2 hours (I also have a masplayer), and I haven't had any graphical errors or crashes since. I couldn't do this when the card was pushed in all the way.
Hope this is of any help to you.