--- dvdauthor-0.6.14.old/src/dvdifo.c
+++ dvdauthor-0.6.14/src/dvdifo.c
@@ -211,7 +211,8 @@
                 write4(buf+p+4,c->vi[i].sector);
             }
         }
-        write4(buf+p+8,c->vi[i-1].lastsector);
+	if (c->vi)
+        	write4(buf+p+8,c->vi[i-1].lastsector);
         p+=12;
     }
     write4(buf+4,p-1);
--- dvdauthor-0.6.14.old/src/dvdvob.c
+++ dvdauthor-0.6.14/src/dvdvob.c
@@ -1415,6 +1415,7 @@
                 s->cells[k].scellid=v;
 
                 if( lastcellid!=v &&
+                    ((v >= 0) && (v < s->vob->numvobus)) &&
                     s->vob->vi[v].firstIfield!=0) {
                     fprintf(stderr,"WARN: GOP may not be closed on cell %d of source %s of pgc %d\n",k+1,s->fname,i+1);
                 }
@@ -1434,6 +1435,10 @@
     for( i=0; i<va->numvobs; i++ ) {
         int cellvobu=0;
         int cellid=0;
+	if (!va->vobs[i])
+		continue;
+	else if (!va->vobs[i]->vi)
+		continue;
         va->vobs[i]->vi[0].vobcellid=1;
         for( j=0; j<va->vobs[i]->numvobus; j++ ) {
             struct vobuinfo *v=&va->vobs[i]->vi[j];