Why does my package start fast then get slower and slower?

Please refer to the second post on the Velocity Scape Forums for the topic: Memory Leak

You can also try changing SQL Server's memory management as the WS user in this post recommends: http://forums.velocityscape.com/default.aspx?g=posts&m=3302#3302

Note: We have not tried this method, it is a user's suggestion from the above forum post. It sounds good in theory though.