Try this patch that's been floating around for a while.

Ani, can you please push this patch to Linus?  It fixes the Radeon
problems for a lot of people.

===== drivers/video/radeonfb.c 1.30 vs edited =====


 25-akpm/drivers/video/radeonfb.c |    2 +-
 1 files changed, 1 insertion(+), 1 deletion(-)

diff -puN drivers/video/radeonfb.c~radeonfb-line_length-fix drivers/video/radeonfb.c
--- 25/drivers/video/radeonfb.c~radeonfb-line_length-fix	Tue Sep 30 16:46:13 2003
+++ 25-akpm/drivers/video/radeonfb.c	Tue Sep 30 16:46:13 2003
@@ -2090,7 +2090,7 @@ static int radeonfb_set_par (struct fb_i
 	
 	}
 	/* Update fix */
-        info->fix.line_length = rinfo->pitch*64;
+        info->fix.line_length = mode->xres_virtual*(mode->bits_per_pixel/8);
         info->fix.visual = rinfo->depth == 8 ? FB_VISUAL_PSEUDOCOLOR : FB_VISUAL_DIRECTCOLOR;
 
 #ifdef CONFIG_BOOTX_TEXT

_