Java 6.0, Windows XP Professional:


I am new to Derby and am using version  My program has been connecting to a database without any problems until today when I get the following 2 chained exceptions:


java.sql.SQLException: Failed to start database 'TestDB', see the next exception for details - Error Code = 40000, SQL State = XJ040

java.sql.SQLException: No class was registered for identifier 24942 - Error Code = 20000, SQL State = XBM0U


What do these errors mean?  They recur even after rebooting the machine involved.