emca fails - cannot drop sysman account

i am trying to recreate the local DBConsole on rdbms 11gR2 running on WIN2k8 sp2

emca - config fails and when i try and drop the sysman account i get the following ora-0600 error

Problem Description
---------------------------------------------------
the following error occiurs when dropping user sysman -
drop user sysman cascade
Error at line 1
ORA-00600: internal error code, arguments: [kzdGenDropStmt], [24], [0], [], [], [], [], [], [], [], [], []

Error Codes
---------------------------------------------------
ora-0600: arguments: [kzdGenDropStmt],

Problem Category/Subcategory
---------------------------------------------------
Other Database Admin (Config, Params, Memory, Dictionary, Scheduler, Processes, Startup/Shutdown, Undo/Rollback, Resource Mgr)/Conventional Backup & Recovery issues