batch insert failing with TokenMetadata AssertionError

I get this during the course of an insert.

ERROR [pool-1-thread-17] 2010-01-20 03:50:40,517 Cassandra.java (line 1096) Internal error processing batch_insert
java.lang.AssertionError
at org.apache.cassandra.locator.TokenMetadata.getToken(TokenMetadata.java:212)
at org.apache.cassandra.locator.AbstractReplicationStrategy.getHintedMapForEndpoints(AbstractReplicationStrategy.java:129)
at org.apache.cassandra.locator.AbstractReplicationStrategy.getHintedEndpoints(AbstractReplicationStrategy.java:76)
at org.apache.cassandra.service.StorageService.getHintedEndpointMap(StorageService.java:1183)
at org.apache.cassandra.service.StorageProxy.insert(StorageProxy.java:101)
at org.apache.cassandra.service.CassandraServer.doInsert(CassandraServer.java:470)
at org.apache.cassandra.service.CassandraServer.batch_insert(CassandraServer.java:445)
at org.apache.cassandra.service.Cassandra$Processor$batch_insert.process(Cassandra.java:1088)
at org.apache.cassandra.service.Cassandra$Processor.process(Cassandra.java:817)
at org.apache.thrift.server.TThreadPoolServer$WorkerProcess.run(TThreadPoolServer.java:253)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:636)