I'm also experiencing this problem when I try to do my backups.
I get nothing out of the ordinary in the alfresco.log file:
10:19:13,841 INFO [org.alfresco.repo.management.subsystems.ChildApplicationContextFactory] Stopping 'imap' subsystem, ID: [default]
10:19:13,841 INFO [org.alfresco.repo.management.subsystems.ChildApplicationContextFactory] Stopped 'imap' subsystem, ID: [default]
10:19:13,842 INFO [org.alfresco.repo.management.subsystems.ChildApplicationContextFactory] Stopping 'Synchronization' subsystem, ID: [default]
10:19:13,842 INFO [org.alfresco.repo.management.subsystems.ChildApplicationContextFactory] Stopped 'Synchronization' subsystem, ID: [default]
10:19:13,873 INFO [org.alfresco.repo.management.subsystems.ChildApplicationContextFactory] Stopping 'thirdparty' subsystem, ID: [default]
10:19:13,874 INFO [org.alfresco.repo.management.subsystems.ChildApplicationContextFactory] Stopped 'thirdparty' subsystem, ID: [default]
10:19:13,881 INFO [org.alfresco.repo.management.subsystems.ChildApplicationContextFactory] Stopping 'Authentication' subsystem, ID: [managed, passthru1]
10:19:13,881 INFO [org.alfresco.repo.management.subsystems.ChildApplicationContextFactory] Stopped 'Authentication' subsystem, ID: [managed, passthru1]
10:19:13,881 INFO [org.alfresco.repo.management.subsystems.ChildApplicationContextFactory] Stopping 'Authentication' subsystem, ID: [managed, ldap1]
10:19:13,882 INFO [org.alfresco.repo.management.subsystems.ChildApplicationContextFactory] Stopped 'Authentication' subsystem, ID: [managed, ldap1]