Use the following if you have this problem. Do not apply this fix if you're running a PowerPC Mac.
Quit X11. Grab this file (2.7MB)) using Safari or command-line wget, then run this command:
sudo tar zxvf xfix.tar.gz -C /
Restart X11. The new binary simply adds a loop of ntohl() to the ARGB image in load_cursor(). A simple modification to quartz-cursor.c, found in X11-0.40.2 -> xc -> programs -> Xserver -> hw -> apple.

