diff --git a/CHANGES.txt b/CHANGES.txt
index 39d2da5ab3..dd729a4c5f 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -10,6 +10,9 @@ dev
  * TcpConnectionManager was holding on to disconnected connections, 
    giving the false indication they were being used. (CASSANDRA-651)
  * Remove duplicated write. (CASSANDRA-662)
+ * Abort bootstrap if IP is already in the token ring (CASSANDRA-663)
+ * increase default commitlog sync period, and wait for last sync to 
+   finish before submitting another (CASSANDRA-668)
 
 
 0.5.0 RC1
diff --git a/conf/storage-conf.xml b/conf/storage-conf.xml
index 8b96057cc4..5445cf6d4b 100644
--- a/conf/storage-conf.xml
+++ b/conf/storage-conf.xml
@@ -314,11 +314,10 @@
   <CommitLogSync>periodic</CommitLogSync>
   <!--
    ~ Interval at which to perform syncs of the CommitLog in periodic mode.
-   ~ Usually the default of 1000ms is fine; increase it only if the
-   ~ CommitLog PendingTasks backlog in jmx shows that you are frequently
-   ~ scheduling a second sync while the first has not yet been processed.
+   ~ Usually the default of 10000ms is fine; increase it if your i/o
+   ~ load is such that syncs are taking excessively long times.
   -->
-  <CommitLogSyncPeriodInMS>1000</CommitLogSyncPeriodInMS>
+  <CommitLogSyncPeriodInMS>10000</CommitLogSyncPeriodInMS>
   <!--
    ~ Delay (in milliseconds) during which additional commit log entries
    ~ may be written before fsync in batch mode.  This will increase
diff --git a/src/java/org/apache/cassandra/db/CommitLog.java b/src/java/org/apache/cassandra/db/CommitLog.java
index 25eed9b5de..1428421519 100644
--- a/src/java/org/apache/cassandra/db/CommitLog.java
+++ b/src/java/org/apache/cassandra/db/CommitLog.java
@@ -202,15 +202,19 @@ public class CommitLog
                 {
                     while (true)
                     {
-                        executor.submit(syncer);
                         try
                         {
+                            executor.submit(syncer).get();
                             Thread.sleep(DatabaseDescriptor.getCommitLogSyncPeriod());
                         }
                         catch (InterruptedException e)
                         {
                             throw new AssertionError(e);
                         }
+                        catch (ExecutionException e)
+                        {
+                            throw new RuntimeException(e);
+                        }
                     }
                 }
             }, "PERIODIC-COMMIT-LOG-SYNCER").start();
diff --git a/src/java/org/apache/cassandra/service/StorageService.java b/src/java/org/apache/cassandra/service/StorageService.java
index dde80ea733..90384f5bf5 100644
--- a/src/java/org/apache/cassandra/service/StorageService.java
+++ b/src/java/org/apache/cassandra/service/StorageService.java
@@ -331,6 +331,11 @@ public final class StorageService implements IEndPointStateChangeSubscriber, Sto
         {
             throw new AssertionError(e);
         }
+        if (tokenMetadata_.isMember(FBUtilities.getLocalAddress()))
+        {
+            String s = "This node is already a member of the token ring; bootstrap aborted. (If replacing a dead node, remove the old one from the ring first.)";
+            throw new UnsupportedOperationException(s);
+        }
         new BootStrapper(replicationStrategy_, FBUtilities.getLocalAddress(), token, tokenMetadata_).startBootstrap(); // handles token update
     }