Please see the following post by Bob Bojanic on the SSIS development team: http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=1855810&SiteID=1

It seems that a change to the CLR has caused binary incompatibilities between assemblies and the VB runtime.

To ensure you are not affected, be sure that you have SQL Server Service Pack 2 (SP2) installed.