Two fixes:

* For constraint mesh-targets, the check for whether the target mesh was in EditMode didn't check to see if the target mesh was the mesh in EditMode. 
Thanks jaguarandi for catching that!

* Bumped up size of buffer for grease-pencil drawing after seeing a program written in 1989 that had a 100 times larger buffer

source/blender/blenkernel/intern/constraint.c

@@ -558,8 +558,8 @@ static void contarget_get_mesh_mat (Object *ob, char *substring, float mat[][4])
 	if (dgroup < 0) return;
 	
 	/* get DerivedMesh */
-	if (G.obedit && G.editMesh) {
-		/* we are in editmode, so get a special derived mesh */
+	if ((G.obedit == ob) && (G.editMesh)) {
+		/* target is in editmode, so get a special derived mesh */
 		dm = CDDM_from_editmesh(G.editMesh, ob->data);
 	}
 	else {

source/blender/src/gpencil.c

@@ -662,7 +662,7 @@ void gpencil_delete_menu (void)
 /* ---------- 'Globals' and Defines ----------------- */
 
 /* maximum sizes of gp-session buffer */
-#define GP_STROKE_BUFFER_MAX	500	
+#define GP_STROKE_BUFFER_MAX	5000	
 
 /* ------ */