Mail Source Agent hangs on LDAP access when switching mailbox. (4233269)

The Mail Source Agent (MSA) hangs after switching one, two or possible more mailboxes. The MSA log (emwmsa.log) contains the following:

"4/6/2010 9:58:37 AM CSession::Logon TraceMsg 4800 Logging on to the mailbox '/o=Org/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients/cn=mailbox' (Server: 'Target_Server', user: 'Domain\Service_Account').
4/6/2010 9:58:50 AM CMBMSwitcher::IsSwitchAllowNow TraceMsg 6203 Checking whether target store is ready to switch.
4/6/2010 9:58:50 AM CMBMSwitcher::IsSwitchAllowNow TraceMsg 6204 Target store is ready to switch.
4/6/2010 9:58:50 AM CMBRedir::MBRedir TraceMsg 1628438538 Starting LDAP asynchronous page search: DN = CN=QMM_Console
4/6/2010 9:58:50 AM CMBRedir::MBRedir TraceMsg 1779433575 Searching object pairs ...
4/6/2010 9:58:50 AM CMBRedir::MBRedir TraceMsg 1628438538 Starting LDAP asynchronous page search: DN = DC=Source_Global_Catalog,DC=com
4/6/2010 9:58:50 AM CMBRedir::MBRedir TraceMsg 1661992963 search was performed
4/6/2010 9:58:51 AM CMBRedir::MBRedir TraceMsg 1628438538 Starting LDAP asynchronous page search: DN = CN=Configuration,DC=Target_Global_Catalog,DC=net"

The MSA is stopped and restarted and the MSA will switch a few more mailboxes before it hangs again.