diff --git a/source/de/anomic/http/httpc.java b/source/de/anomic/http/httpc.java
index c9b1f9f1f..747caa9e6 100644
--- a/source/de/anomic/http/httpc.java
+++ b/source/de/anomic/http/httpc.java
@@ -92,7 +92,13 @@ public class httpc {
     private static HashMap nameCacheHit = new HashMap();
     //private static HashSet nameCacheMiss = new HashSet();
     
-    public static String dnsResolve(String host) {
+    static {
+	// set time-out of InetAddress.getByName cache ttl
+	java.security.Security.setProperty("networkaddress.cache.ttl" , "60");
+        java.security.Security.setProperty("networkaddress.cache.negative.ttl" , "0");
+    }
+
+    private static String dnsResolveX(String host) {
         // looks for the ip of host <host> and returns ip number as string
         String ip = (String) nameCacheHit.get(host);
         if (ip != null) return ip;
@@ -111,6 +117,18 @@ public class httpc {
         return null;
     }
     
+    public static String dnsResolve(String host) {
+        String ip = null;
+        for (int i = 0; i < 50; i++) {
+            ip = dnsResolveX(host);
+            if (ip != null) {
+                //if (i > 0) System.out.println(i + " attempts for " + host);
+                return ip;
+            }
+        }
+        return ip;
+    }
+
     public static boolean dnsFetch(String host) {
         // looks for the ip of host <host> and returns false if the host was in the cache
         // if it is not in the cache the ip is fetched and this resturns true
diff --git a/source/de/anomic/kelondro/kelondroDyn.java b/source/de/anomic/kelondro/kelondroDyn.java
index 0d2808290..6102a5fdc 100644
--- a/source/de/anomic/kelondro/kelondroDyn.java
+++ b/source/de/anomic/kelondro/kelondroDyn.java
@@ -158,8 +158,11 @@ public class kelondroDyn extends kelondroTree {
 	    String k;
 	    String v;
 	    int c;
+	    byte[][] nt;
 	    while (ri.hasNext()) {
-		g = ((byte[][]) ri.next())[0];
+		nt = (byte[][]) ri.next();
+		if (nt == null) return null;
+		g = nt[0];
 		if (g == null) return null;
 		k = new String(g, 0, keylen);
 		v = new String(g, keylen, counterlen);
diff --git a/source/de/anomic/kelondro/kelondroMap.java b/source/de/anomic/kelondro/kelondroMap.java
index a92186c41..7044b1677 100644
--- a/source/de/anomic/kelondro/kelondroMap.java
+++ b/source/de/anomic/kelondro/kelondroMap.java
@@ -96,6 +96,7 @@ public class kelondroMap {
             Map map;
             while (it.hasNext()) {
                 key = (String) it.next();
+		//System.out.println("kelondroMap: enumerating key " + key);
                 map = get(key);
                 
                 if (sortfields != null) for (int i = 0; i < sortfields.length; i++) {
@@ -422,6 +423,7 @@ public class kelondroMap {
             }
             try {
                 Map map = get(nextKey);
+                if (map == null) return null;
                 map.put("key", nextKey);
                 return map;
             } catch (IOException e) {
diff --git a/source/de/anomic/kelondro/kelondroTree.java b/source/de/anomic/kelondro/kelondroTree.java
index 24a91f9a9..fcf6f60c3 100644
--- a/source/de/anomic/kelondro/kelondroTree.java
+++ b/source/de/anomic/kelondro/kelondroTree.java
@@ -251,12 +251,14 @@ public class kelondroTree extends kelondroRecords implements Comparator {
 	Node nextNode = null;
         boolean up, rot;
         LinkedList nodeStack;
+	int count;
         
 	public nodeIterator(boolean up, boolean rotating) throws IOException {
             this(up, rotating, (up) ? firstNode() : lastNode());
 	}
         
 	public nodeIterator(boolean up, boolean rotating, Node start) throws IOException {
+	    this.count = 0;
             this.up = up;
             this.rot = rotating;
             this.nextNode = start;
@@ -289,7 +291,9 @@ public class kelondroTree extends kelondroRecords implements Comparator {
 	}
 
         public Object next() {
+	    count++;
             if (nextNode == null) return null;
+	    if (count > size()) return null;
             Object ret = nextNode;
             
             // middle-case
@@ -890,7 +894,9 @@ public class kelondroTree extends kelondroRecords implements Comparator {
         
         public Object next() {
             try {
-                return ((Node) nodeIterator.next()).getValues();
+		Node nextNode = (Node) nodeIterator.next();
+		if (nextNode == null) return null; // this is an error case of the nodeIterator
+                return nextNode.getValues();
             } catch (IOException e) {
                 return null;
             }