diff --git a/html/inc/boinc_db.inc b/html/inc/boinc_db.inc
index 47aba87948..87b7c5a8fa 100644
--- a/html/inc/boinc_db.inc
+++ b/html/inc/boinc_db.inc
@@ -473,7 +473,7 @@ class BoincPrivateMessage {
         $db = BoincDb::get();
         return $db->delete($this, 'private_messages');
     }
-    function delete_aux($clause) {
+    static function delete_aux($clause) {
         $db = BoincDb::get();
         return $db->delete_aux('private_messages', $clause);
     }
diff --git a/html/inc/forum.inc b/html/inc/forum.inc
index ddb3e2202e..fec13558e7 100644
--- a/html/inc/forum.inc
+++ b/html/inc/forum.inc
@@ -926,6 +926,7 @@ function forum_delete_user($user) {
     }
     $p = BoincForumPrefs::lookup_userid($user->id);
     if ($p) $p->delete();
+    BoincForumLogging::delete_aux("userid=$user->id");
 }
 
 function move_post($post, $old_thread, $old_forum, $new_thread, $new_forum) {
diff --git a/html/ops/delete_spammers.php b/html/ops/delete_spammers.php
index 7cf9c7c08d..d504ae7a50 100755
--- a/html/ops/delete_spammers.php
+++ b/html/ops/delete_spammers.php
@@ -70,6 +70,8 @@ function delete_user($user) {
     }
     delete_profile($user);
     forum_delete_user($user);
+    BoincPrivateMessage::delete_aux("userid=$user->id or senderid=$user->id");
+    BoincNotify::delete_aux("userid=$user->id");
     $q = "delete from user where id=$user->id";
     mysql_query($q);
 }
diff --git a/html/user/pm.php b/html/user/pm.php
index 092c91e24f..5134155828 100644
--- a/html/user/pm.php
+++ b/html/user/pm.php
@@ -90,6 +90,11 @@ function do_inbox($logged_in_user) {
         echo "<tr><th>".tra("Subject")."</th><th>".tra("Sender and date")."</th><th>".tra("Message")."</th></tr>\n";
         $i = 0;
         foreach($msgs as $msg) {
+            $sender = BoincUser::lookup_id($msg->senderid);
+            if (!$sender) {
+                $msg->delete();
+                continue;
+            }
             $i++;
             $class = ($i%2)? "row0": "row1";
             echo "<tr class=$class>\n";
@@ -98,7 +103,7 @@ function do_inbox($logged_in_user) {
                 $msg->update("opened=1");
             }
             echo "<td valign=top> $checkbox $msg->subject </td>\n";
-            echo "<td valign=top>".user_links(BoincUser::lookup_id($msg->senderid));
+            echo "<td valign=top>".user_links($sender);
             show_block_link($msg->senderid);
             echo "<br>".time_str($msg->date)."</td>\n";
             echo "<td valign=top>".output_transform($msg->content, $options)."<p>";