OPM regularly stops working

Hi.
opm regularly quits with the following error:

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, admin@india.adventnet.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
Apache/2.0.47 (Win32) mod_jk/1.2.3-dev Server at server Port 80

the last entries in wrapper.log are:

ERROR | wrapper | 2005/12/19 01:31:35 | JVM appears hung: Timed out waiting for signal from JVM.
STATUS | wrapper | 2005/12/19 01:31:36 | Dumping JVM state.
...
STATUS | wrapper | 2005/12/19 01:31:45 | Launching a JVM...
INFO | jvm 2 | 2005/12/19 01:31:53 | Wrapper (Version 3.1.1) http://wrapper.tanukisoftware.org
INFO | jvm 2 | 2005/12/19 01:31:53 |
INFO | jvm 2 | 2005/12/19 01:31:54 | WebServer Port is Occupied.

i need to restart the manage engine service and kill the apache processes to start opmanager again.
This happens 1-2 days a week. the java.exe process needs 40-60% cpu all the time, but cpu and ram shouldn't be the bottleneck.

My configuration:
windows 2003 sp1
768mb ram
no other software is running on that machine
opm monitors 150 devices

thanks for help.