Index: driver/screens.c
===================================================================
RCS file: /cvsroot/xscreensaver/driver/screens.c,v
retrieving revision 1.7
diff -u -r1.7 screens.c
--- driver/screens.c	8 Jul 2008 05:22:46 -0000	1.7
+++ driver/screens.c	24 Jul 2008 15:52:14 -0000
@@ -342,7 +342,7 @@
 
   for (i = 0, j = 0; i < ScreenCount (dpy); i++)
     {
-      Screen *screen = ScreenOfDisplay (dpy, j);
+      Screen *screen = ScreenOfDisplay (dpy, i);
 
       if (! new_randr_p)  /* RANDR 1.0 */
         {
@@ -624,6 +624,7 @@
       if (i != j &&
           monitors[i]->sanity == S_SANE &&
           monitors[j]->sanity == S_SANE &&
+          monitors[i]->screen == monitors[j]->screen &&
           X2 >= X1 &&
           Y2 >= Y1 &&
           (X2+W2) <= (X1+W1) &&
@@ -648,6 +649,7 @@
       {
         if (monitors[i]->sanity != S_SANE) continue; /* already marked */
         if (monitors[j]->sanity != S_SANE) continue;
+        if (monitors[i]->screen != monitors[j]->screen) continue;
 
         if (monitors_overlap_p (monitors[i], monitors[j]))
           {
@@ -656,17 +658,15 @@
           }
       }
 
-  /* Finally, make sure all monitors are enclosed by their X screen.
+  /* Finally, make sure all monitors have sane positions and sizes.
      Xinerama sometimes reports 1024x768 VPs at -1936862040, -1953705044.
    */
   for (i = 0; i < count; i++)
     {
-      int sw = WidthOfScreen (monitors[i]->screen)  * 2;
-      int sh = HeightOfScreen (monitors[i]->screen) * 2;
       if (monitors[i]->sanity != S_SANE) continue; /* already marked */
-      if (X1    <  0 || Y1    <  0 || 
-          W1    <= 0 || H1    <= 0 || 
-          X1+W1 > sw || Y1+H1 > sh)
+      if (X1    <  0      || Y1    <  0 || 
+          W1    <= 0      || H1    <= 0 || 
+          X1+W1 >= 0x7FFF || Y1+H1 >= 0x7FFF)
         {
           monitors[i]->sanity = S_OFFSCREEN;
           monitors[i]->enemy = 0;