I used IE to open Oracle Enterprise Manager, last week it is fine. But
today I try again (https://localhost/em/console/logon/logon) it didn't
work.

I opened Oracle_Home\bin\emctl.msg:
HealthMonitor 2009-9-14 PM12:15:39 Job Dispatcher error: Could not get
connection
HealthMonitor 2009-9-29 PM04:21:10 XMLLoader error: Exiting app due to
out of memory condition
HealthMonitor 2009-9-29 PM04:53:01 CacheManager error: Exiting app due
to out of memory condition
HealthMonitor 2009-10-7 PM03:12:19 XMLLoader error: Exiting app due to
out of memory condition
HealthMonitor 2009-10-7 PM03:15:29 OMS Service Driver error: Exiting
app due to out of memory condition
HealthMonitor 2009-10-8 PM02:08:20 CacheManager error: Exiting app due
to out of memory condition
HealthMonitor 2009-10-8 PM02:10:17 XMLLoader error: Exiting app due to
out of memory condition
HealthMonitor 2009-10-8 PM02:23:09 OMS Service Driver error: Exiting
app due to out of memory condition

Please help!!! Many THANKS!!!