AssertionError in MappedFileDataInput.skipBytes when slicing a large number of keys

i'm getting the following error when performing a range query that is supposed to return a large number of keys:

ERROR [ROW-READ-STAGE:9] 2010-03-07 03:54:49,672 CassandraDaemon.java (line 78) Fatal exception in thread Thread[ROW-READ-STAGE:9,5,main]
java.lang.AssertionError
at org.apache.cassandra.io.util.MappedFileDataInput.skipBytes(MappedFileDataInput.java:104)
at org.apache.cassandra.io.SSTableReader.getPosition(SSTableReader.java:382)
at org.apache.cassandra.io.SSTableReader.getFileDataInput(SSTableReader.java:481)
at org.apache.cassandra.db.filter.SSTableSliceIterator.<init>(SSTableSliceIterator.java:54)
at org.apache.cassandra.db.filter.SliceQueryFilter.getSSTableColumnIterator(SliceQueryFilter.java:63)
at org.apache.cassandra.db.ColumnFamilyStore.getTopLevelColumns(ColumnFamilyStore.java:851)
at org.apache.cassandra.db.ColumnFamilyStore.getColumnFamily(ColumnFamilyStore.java:771)
at org.apache.cassandra.db.ColumnFamilyStore.getColumnFamily(ColumnFamilyStore.java:740)
at org.apache.cassandra.db.ColumnFamilyStore.getRangeSlice(ColumnFamilyStore.java:1040)
at org.apache.cassandra.service.RangeSliceVerbHandler.doVerb(RangeSliceVerbHandler.java:41)
at org.apache.cassandra.net.MessageDeliveryTask.run(MessageDeliveryTask.java:40)
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:619)