Error while detecting start profile for instance with ID _u

I am upgrading a SAP Java instance and am getting the error shown in the log below. There are not backup profile files in the profiles directory.

The string _u does not exist in the default, start or instance profile for instance SCS01.

Please can you suggest what the issue might be?

Mar 13, 2010 12:09:01 PM [Info]: com.sap.sdt.ucp.phases.AbstractPhaseType.initializexAbstractPhaseType.javax758x [Thread[main,5,main]]: Phase PREPARE/INIT/DETERMINE_PROFILES has been started. Mar 13, 2010 12:09:01 PM [Info]: com.sap.sdt.ucp.phases.AbstractPhaseType.initializexAbstractPhaseType.javax759x [Thread[main,5,main]]: Phase type is com.sap.sdt.j2ee.phases.PhaseTypeDetermineProfiles. Mar 13, 2010 12:09:01 PM [Info]: ...ap.sdt.j2ee.phases.PhaseTypeDetermineProfiles.checkVariablesxPhaseTypeDetermineProfiles.javax284x [Thread[main,5,main]]: All 4 required variables exist in variable handler. Mar 13, 2010 12:09:01 PM [Info]: ....j2ee.tools.sysinfo.AbstractInfoController.updateProfileVariablexAbstractInfoController.javax302x [Thread[main,5,main]]: Parameter /J2EE/StandardSystem/DefaultProfilePath has been detected. Parameter value is \server1\SAPMNT\PI7\SYS\profile\DEFAULT.PFL. Mar 13, 2010 12:09:01 PM [Info]: com.sap.sdt.j2ee.tools.sysinfo.ProfileDetector.detectInstancexProfileDetector.javax340x [Thread[main,5,main]]: Instance SCS01 with profile \server1\SAPMNT\PI7\SYS\profile\PI7_SCS01_server1, start profile \server1\SAPMNT\PI7\SYS\profile\START_SCS01_server1, and host server1 has been detected. Mar 13, 2010 12:09:01 PM [Error]: com.sap.sdt.ucp.phases.AbstractPhaseType.doExecutexAbstractPhaseType.javax862x [Thread[main,5,main]]: Exception has occurred during the execution of the phase. Mar 13, 2010 12:09:01 PM [Error]: com.sap.sdt.j2ee.tools.sysinfo.ProfileDetector.detectInstancexProfileDetector.javax297x [Thread[main,5,main]]: Error while detecting start profile for instance with ID _u. Mar 13, 2010 12:09:01 PM [Info]: com.sap.sdt.ucp.phases.AbstractPhaseType.cleanupxAbstractPhaseType.javax905x [Thread[main,5,main]]: Phase PREPARE/INIT/DETERMINE_PROFILES has been completed. Mar 13, 2010 12:09:01 PM [Info]: com.sap.sdt.ucp.phases.AbstractPhaseType.cleanupxAbstractPhaseType.javax906x [Thread[main,5,main]]: Start time: 2010/03/13 12:09:01. Mar 13, 2010 12:09:01 PM [Info]: com.sap.sdt.ucp.phases.AbstractPhaseType.cleanupxAbstractPhaseType.javax908x [Thread[main,5,main]]: End time: 2010/03/13 12:09:01. Mar 13, 2010 12:09:01 PM [Info]: com.sap.sdt.ucp.phases.AbstractPhaseType.cleanupxAbstractPhaseType.javax909x [Thread[main,5,main]]: Duration: 0:00:00.078. Mar 13, 2010 12:09:01 PM [Info]: com.sap.sdt.ucp.phases.AbstractPhaseType.cleanupxAbstractPhaseType.javax910x [Thread[main,5,main]]: Phase status is error.