diff --git a/frysk-core/frysk/hpd/CLI.java b/frysk-core/frysk/hpd/CLI.java
index 3c14b2e..d79e557 100644
--- a/frysk-core/frysk/hpd/CLI.java
+++ b/frysk-core/frysk/hpd/CLI.java
@@ -123,6 +123,7 @@ public class CLI {
 	    return topLevelCommand.complete(this, new Input(buffer), cursor,
 					    candidates);
 	} catch (RuntimeException e) {
+	    // XXX - FIXME - What if this is something fatal?
 	    return -1;
 	}
     }
@@ -142,7 +143,7 @@ public class CLI {
 	    outWriter.print("Attached to process ");
 	    outWriter.println(attached);
         } catch (InterruptedException ie) {
-            addMessage("Attach interrupted.", Message.TYPE_ERROR);
+            addMessage("Attach interrupted.", Message.TYPE_ERROR, ie);
             return;
         } finally {
             synchronized (this) {
@@ -253,19 +254,14 @@ public class CLI {
 		    topLevelCommand.interpret(this, command);
                 }
             }
-            catch (NullPointerException e) {
-                e.printStackTrace();
-                String msg = "";
-                if (e.getMessage() != null)
-                    msg = e.getMessage();
-
-                addMessage(msg, Message.TYPE_DBG_ERROR);
-            }
+            catch (InvalidCommandException ice) {
+                addMessage(ice.getMessage(), Message.TYPE_ERROR);
+	    }
             catch (RuntimeException e) {
-                String msg = "";
-                if (e.getMessage() != null)
-                    msg = e.getMessage();
-                addMessage(msg, Message.TYPE_ERROR);
+                String msg = e.getMessage();
+                if (msg == null || msg.equals(""))
+                    msg = e.toString();
+                addMessage(msg, Message.TYPE_DBG_ERROR, e);
             }
             flushMessages();
         }
@@ -280,6 +276,10 @@ public class CLI {
         addMessage(new Message(msg, type));
     }
 
+    void addMessage(String msg, int type, Throwable exc) {
+        addMessage(new Message(msg, type, exc));
+    }
+
     private void flushMessages() {
         for (Iterator iter = messages.iterator(); iter.hasNext();) {
             Message tempmsg = (Message) iter.next();
@@ -293,8 +293,12 @@ public class CLI {
             if (prefix != null)
                 outWriter.print(prefix);
             outWriter.println(tempmsg.getMessage());
+	    Throwable exc = tempmsg.getException();
+	    if (exc != null)
+		exc.printStackTrace(outWriter);
             iter.remove();
         }
+	outWriter.flush();
     }
 
     PTSet createSet(String set) {
diff --git a/frysk-core/frysk/hpd/EvalCommands.java b/frysk-core/frysk/hpd/EvalCommands.java
index 5c69032..d9679db 100644
--- a/frysk-core/frysk/hpd/EvalCommands.java
+++ b/frysk-core/frysk/hpd/EvalCommands.java
@@ -96,7 +96,10 @@ abstract class EvalCommands extends ParameterizedCommand {
 	    try {
 		result = cli.parseValue(task, expression, options.dumpTree);
 	    } catch (RuntimeException nnfe) {
-		cli.addMessage(nnfe.getMessage(), Message.TYPE_ERROR);
+		String msg = nnfe.getMessage();
+		if (msg == null || msg.equals(""))
+		    msg = nnfe.toString();
+		cli.addMessage(msg, Message.TYPE_ERROR, nnfe);
 		continue;
 	    }
 
diff --git a/frysk-core/frysk/hpd/Message.java b/frysk-core/frysk/hpd/Message.java
index 933305f..aeb4ed2 100644
--- a/frysk-core/frysk/hpd/Message.java
+++ b/frysk-core/frysk/hpd/Message.java
@@ -49,17 +49,39 @@ class Message
 	public static int TYPE_NORMAL = 3;
 	public static int TYPE_VERBOSE = 4;
 
-	String msg = null;
-	int type = 0;
+	private final String msg;
+	private final int type;
+        private final Throwable exc;
 
-	public Message (String msg, int type)
+        /**
+	 * Creates a new Message with the given message and type
+	 * and no exception.
+	 */
+        public Message (String msg, int type)
+        {
+	    this(msg, type, null);
+	}  
+        /**
+	 * Creates a new Message with the given message and type.
+	 * The message cannot be null or empty. The exception is optional
+	 * and may be null.
+	 */
+        public Message (String msg, int type, Throwable exc)
 	{
+	        if (msg == null)
+		    throw new NullPointerException("null msg");
+
+	        if (msg.equals(""))
+		    throw new IllegalArgumentException("empty msg");
+
 		this.msg = msg;
 
 		if (type < TYPE_DBG_ERROR || type > TYPE_VERBOSE)
 			throw new IllegalArgumentException("Debugger message created with illegal type.");
 		else
 			this.type = type;
+
+		this.exc = exc;
 	}
 
 	public String getMessage()
@@ -71,4 +93,9 @@ class Message
 	{
 		return type;
 	}
+
+        public Throwable getException()
+        {
+	        return exc;
+        }
 }
diff --git a/frysk-core/frysk/hpd/PlocationCommand.java b/frysk-core/frysk/hpd/PlocationCommand.java
index 225cc09..61ced31 100644
--- a/frysk-core/frysk/hpd/PlocationCommand.java
+++ b/frysk-core/frysk/hpd/PlocationCommand.java
@@ -77,7 +77,10 @@ class PlocationCommand extends ParameterizedCommand {
             try {
                 result = cli.parseValue(task, sInput);	  
             } catch (RuntimeException nnfe) {
-                cli.addMessage(nnfe.getMessage(), Message.TYPE_ERROR);
+		String msg = nnfe.getMessage();
+		if (msg == null || msg.equals(""))
+		    msg = nnfe.toString();
+                cli.addMessage(msg, Message.TYPE_ERROR, nnfe);
                 continue;
             }
 	    result.getLocation().toPrint(cli.outWriter);