To get the archive manager going you may need to run ArchMgr –repair from command line. To figure out why it crashed, you can look in the log files as Silvio mentioned. There is also this fix in H02 for 9.3 which helped clients that reported this issue (I would recommend installing H03 though, as it has more fixes):
Symptom: The Archive Manager could crash seemingly randomly when processing inactive CORBA clients.
Resolution: The Archive Manager will no longer crash when processing inactive CORBA clients.
(H02, 299705, 21732126-1)
(H02, 298369, 21732126-1)
And you could always open a case to have us review the info if need be.
Cheers
Jay