preferences.xml file gets corrupted

Hi There,

We have lots of concurrency issues where queues get locked up and we need to re-start the scheduler.
When we do sometimes and we try to start it back up we get errors like such:

2011-11-30 09:20:36,086 [main] DEBUG com.softtreetech.jscheduler.JSchedulerStarter - JVM version: 1.5.0_20-b02
2011-11-30 09:20:36,087 [main] DEBUG com.softtreetech.jscheduler.JSchedulerStarter - main(...) : start
2011-11-30 09:20:36,087 [main] DEBUG com.softtreetech.jscheduler.JSchedulerStarter - startup() : start
2011-11-30 09:20:36,214 [main] DEBUG com.softtreetech.jscheduler.JSchedulerStarter - startup() : creating business objects
2011-11-30 09:20:36,309 [main] DEBUG com.softtreetech.jscheduler.JSchedulerStarter - startup() : creating UI controller
2011-11-30 09:20:36,391 [main] DEBUG com.softtreetech.jscheduler.JSchedulerStarter - startup() : initializing business objects
2011-11-30 09:20:36,406 [main] DEBUG com.softtreetech.jscheduler.business.preferences.AbstractPrefDatabase - Creating backup for preferences file preferences.xml
2011-11-30 09:20:36,408 [main] DEBUG com.softtreetech.jscheduler.business.preferences.AbstractPrefDatabase - Preferences file has been copied to preferences.bak
2011-11-30 09:20:37,638 [main] DEBUG com.softtreetech.jscheduler.JSchedulerStarter - startup() : XML document structures must start and end within the same entity.
2011-11-30 09:20:42,085 [main] DEBUG com.softtreetech.jscheduler.JSchedulerStarter - startup() : Setting shutdown event hook
2011-11-30 09:20:42,086 [main] DEBUG com.softtreetech.jscheduler.JSchedulerStarter - startup() : creating user interface...
2011-11-30 09:20:42,459 [main] FATAL com.softtreetech.jscheduler.JSchedulerStarter - startup() :
java.lang.IllegalStateException: pref db is not opened.
at com.softtreetech.jscheduler.business.preferences.AbstractPrefDatabase.checkOpened(Unknown Source)
at com.softtreetech.jscheduler.business.preferences.AbstractPrefDatabase.getIdsByType(Unknown Source)
at com.softtreetech.jscheduler.business.preferences.SettingsImpl.getOptions(Unknown Source)
at com.softtreetech.jscheduler.ui.controller.UIController.setTitle(Unknown Source)
at com.softtreetech.jscheduler.ui.controller.UIController.createMainFrame(Unknown Source)
at com.softtreetech.jscheduler.ui.controller.MasterController.createMainFrame(Unknown Source)
at com.softtreetech.jscheduler.JSchedulerStarter.startup(Unknown Source)
at com.softtreetech.jscheduler.JSchedulerStarter.main(Unknown Source)
2011-11-30 09:20:47,131 [main] DEBUG com.softtreetech.jscheduler.business.Master - shutdown() start
2011-11-30 09:20:47,132 [main] DEBUG com.softtreetech.jscheduler.business.runner.JobExecutorImpl - killAll() start
2011-11-30 09:20:47,132 [main] FATAL com.softtreetech.jscheduler.JSchedulerStarter - java.lang.IllegalStateException: pref db is not opened.

Is there any way to prevent this?
When it does go down, it can take me up to an hour or so before it will start back up.

What I wind up having to do is to restore the file. I take a nightly backup of the file.

Let me know your thoughts on this.

Thanks.