SQL Server 2005 - Crash (Services Stop)

Hello,
I'm having a problem with my SQL Server 2005 Enterprise box.  Over night
it stops the services (Engine & Agent).  I know that it is caused by a SSIS
package that runs @ that time.  The funny thing is that this package
sometimes run without any problem and sometimes crashes the server; it
doesn't make sense.  That package simlpy import data from a legacy system
(AS400).  When looking at the event log, here is the error message:

Description:
SQL Server Assertion: File: <lckmgr.cpp>, line=9421 Failed Assertion = 'NULL
== m_lockList.Head ()'. This error may be timing-related. If the error
persists after rerunning the statement, use DBCC CHECKDB to check the
database for structural integrity, or restart the server to ensure in-memory
data structures are not corrupted.

For more information, see Help and Support Center at
http://go.microsoft.com/fwlink/events.asp.
Data:

Any help would be greatly appreciated.  Thanks.