Always see strange error in logs on cassandra 1.1.6

[Михаил Колесников <mi...@startpack.ru>]

Hi.

After updating Cassandra from 1.1.5 to 1.1.6. Every schema updates ends with strange error exception in system.log and I must to restart nodes in cluster for whom `describe cluster` says that nodes are unreachable.
Neither `nodetool repair` or `nodetool upgragesstables` doesn't help. Only double restarting of service helps, the first restart throws the same error, the second restart doesn't and starts node normally.

Error log:
ERROR [FlushWriter:8] 2012-11-28 10:57:50,503 AbstractCassandraDaemon.java (line 135) Exception in thread Thread[FlushWriter:8,5,main]
java.lang.AssertionError: Keys must not be empty
        at org.apache.cassandra.io.sstable.SSTableWriter.beforeAppend(SSTableWriter.java:133)
        at org.apache.cassandra.io.sstable.SSTableWriter.append(SSTableWriter.java:176)
        at org.apache.cassandra.db.Memtable.writeSortedContents(Memtable.java:295)
        at org.apache.cassandra.db.Memtable.access$600(Memtable.java:48)
        at org.apache.cassandra.db.Memtable$5.runMayThrow(Memtable.java:316)
        at org.apache.cassandra.utils.WrappedRunnable.run(WrappedRunnable.java:30)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
        at java.lang.Thread.run(Thread.java:662)

Best regards
-Michael