Overscan issues with X.Org

Vital Stats:
Kernel Image: mikep5-zImage-2.6.32.mini.480p(NTSC).elf
Distribution: debian-lenny-5.0+whiite-1.10.tar.bz2
Compiled xf86-video-cube driver(http://gc-linux.cvs.sourceforge.net/viewvc/gc-linux/xf86-video-cube/) with Wiibrewfan4's patches.

--- cube_driver.c	2008-11-05 06:14:51.000000000 -0600
+++ cube_driver_patched.c	2011-03-15 17:16:43.000000000 -0500
@@ -948,7 +948,7 @@
   {
     xf86DrvMsg(pScrn->scrnIndex, X_ERROR, 
                "Selected width = %d and height = %d is not supported by cube/wii\n", width, height);
-    return FALSE;
+    return TRUE;
   }
 
   refresh = (mode->Clock * 1.0e3)/((double)(mode->HTotal) * 
@@ -1163,8 +1163,8 @@
 {
   BoxRec box;
   box.x1 = 0;
-  box.x2 = 640;
+  box.x2 = pScrn->currentMode->HDisplay;
   box.y1 = 0;
-  box.y2 = 480;
+  box.y2 = pScrn->currentMode->VDisplay;
   CUBERefreshArea(pScrn, 1, &box);
 }

startx fails with this line in xorg.conf.
Modeline "ntsc_60" 23.72 640 656 720 800 460 577 580 593 -HSync +Vsync

Backtrace:
0: /usr/bin/X11/X(xf86SigHandler+0x98) [0x100a5898]
1: [0x100344]
2: /usr/bin/X11/X [0x10157b30]
3: /usr/lib/xorg/modules//libshadowfb.so [0xf71b238]
4: /usr/bin/X11/X(miHandleValidateExposures+0x84) [0x10112e44]
5: /usr/bin/X11/X(miSlideAndSizeWindow+0xa78) [0x10114608]
6: /usr/bin/X11/X(compResizeWindow+0xd0) [0x100dd2f0]
7: /usr/bin/X11/X(ConfigureWindow+0x684) [0x10033144]
8: /usr/bin/X11/X(ProcConfigureWindow+0xb8) [0x100497a8]
9: /usr/bin/X11/X [0x101306f0]
10: /usr/bin/X11/X(Dispatch+0x4a0) [0x1004a4b0]
11: /usr/bin/X11/X(main+0x474) [0x1002bc74]
12: /lib/libc.so.6 [0xfb93704]
13: /lib/libc.so.6 [0xfb938c0]

Fatal server error:
Caught signal 11.  Server aborting

startx works fine with
Modeline "ntsc_60" 23.72 640 656 720 800 480 577 580 593 -HSync +Vsync

Any suggestions on resolving the crash, or other ideas about overscan correction?