Oracle 9 and 10 should have an object identifier at the end of the
error to give you a clue.  You can also use various scripts or tools
to see what is locked.  It helps to say your exact version, there's an
O9 bug having to do with compiling pl/sql, another one with smon
locking undo (which might show up if you have read consistency issues
trying to export while others update).  10.1 has a bug if you are
doing any DDL while exporting, see Note:298968.1.

Metalink Note: 169139.1 is the basic description on how to figure out
the problem.  It's best to do exports when no one is on, and check the
utilities manual for the consistent parameter.

jg
--
@home.com is bogus.  “We have a saying out here in rural California:
'If you need a hip replacement, commit a felony,' ” - Charles
Guenther, noting that prisons are under court order to improve medical
care, while the state isn't paying Medi-Cal hospitals because of the
budget deadlock.