Index: bridges.c
===================================================================
--- bridges.c	(revision 8764)
+++ bridges.c	(working copy)
@@ -2097,7 +2097,7 @@
     if (button == LEFT_BUTTON || button == RIGHT_BUTTON) {
         if (!INGRID(state, gx, gy)) return NULL;
         ui->cur_visible = 0;
-        if ((ggrid & G_ISLAND) && !(ggrid & G_MARK)) {
+        if ((ggrid & G_ISLAND)) {
             ui->dragx_src = gx;
             ui->dragy_src = gy;
             return "";
@@ -2606,7 +2606,8 @@
         force = 1;
     }
 
-    if (ui->dragx_src != -1 && ui->dragy_src != -1) {
+    v = INGRID(state,ui->dragx_src,ui->dragy_src) ? GRID(state,ui->dragx_src,ui->dragy_src) : 0;
+    if (ui->dragx_src != -1 && ui->dragy_src != -1 && !(v & G_MARK)) {
         ds->dragging = 1;
         is_drag_src = INDEX(state, gridi, ui->dragx_src, ui->dragy_src);
         assert(is_drag_src);