SSIS packages fail with Pending Execution Status

My packages have been running on our production environment for a couple of weeks until they started failing with very little information apart from packages having a pending execution status. All packages fail regardless of the user executing them e.g. myself or the SQL Agent service account. There is a cryptic error message in the windows log about activation permissions for the SQL Integration Services. Setting permissions for the accounts calling the package makes no difference, I managed to get them working by repairing the SQL Server installation I couldn't see what repairs it had made. Now following a reboot of the server all packages refuse to run. I have managed to get them to work by repairing the SQL Server installation again. This is obviously not a scalable solution. I suspect that some group policy setting is overriding a local security setting and this is why it happens after some time or after a reboot. Has anybody come across this issue before or have any ideas where to look.