Update to latest Bootstrap 3 (RC2)

assets/less/bootstrap/modals.less

@@ -29,7 +29,7 @@
     .translate(0, -25%);
     .transition-transform(~"0.3s ease-out");
   }
-  &.fade.in  .modal-dialog { .translate(0, 0)}
+  &.in .modal-dialog { .translate(0, 0)}
 }
 
 // Shell div to position the modal with bottom padding
@@ -49,7 +49,7 @@
   border: 1px solid @modal-content-border-color;
   border-radius: @border-radius-large;
   .box-shadow(0 3px 9px rgba(0,0,0,.5));
-  .background-clip(padding-box);
+  background-clip: padding-box;
   // Remove focus outline from opened modal
   outline: none;
 }
@@ -65,7 +65,7 @@
   background-color: @modal-backdrop-bg;
   // Fade for backdrop
   &.fade { .opacity(0); }
-  &.fade.in { .opacity(.5); }
+  &.in { .opacity(.5); }
 }
 
 // Modal header