"An internal error was identified by RawStore module"?

[Barnet Wagman]

Does anyone have an idea of what "An internal error was identified by 
RawStore module" might mean?  It was thrown by a "DROP TABLE" command.  
The stack was

SQL Exception: An internal error was identified by RawStore module.
       at org.apache.derby.impl.jdbc.Util.generateCsSQLException(Util.java)
       at 
org.apache.derby.impl.jdbc.TransactionResourceImpl.wrapInSQLException(TransactionResourceImpl.java)
       at 
org.apache.derby.impl.jdbc.TransactionResourceImpl.handleException(TransactionResourceImpl.java)
       at 
org.apache.derby.impl.jdbc.EmbedConnection.handleException(EmbedConnection.java)
       at 
org.apache.derby.impl.jdbc.ConnectionChild.handleException(ConnectionChild.java)
       at 
org.apache.derby.impl.jdbc.EmbedStatement.execute(EmbedStatement.java)
       at 
org.apache.derby.impl.jdbc.EmbedStatement.executeUpdate(EmbedStatement.java)