Package could not be loaded

Hello,

I'm having an issue with executing a package using SQL Server Agent. I have 7 packages that I've got 7 separate jobs for. I also have 7 separate stored procedures that each call the appropriate job using sp_start_job. We are using BizTalk to execute these 7 stored procedures, which in turn start a job, which in turn will call an SSIS Package to run. When we execute the 7 jobs spaced apart, i.e. 2 or 3 seconds apart, they all run fine. When we BizTalk executes them all at the same time, within milliseconds of each other, sometimes they all run fine, sometimes a few of the SSIS Packages end up with the error "The Package could not be loaded" in the SQL Server Agent history log.
Is there an issue when trying to execute multiple Packages all at the same time? It's not like I'm calling the same package 2 times, they are all different packages. Can anyone shed any light on this?
Thanks,
Andy

There is no SSIS issue with doing this (as far as I am aware) so you might want to post this in the agent forum as well.

Thanks,
Matt