SQL server 2005 slowing down after a while

Oopps! Upgrade your browser pretty please.Oopps! Upgrade your browser pretty please.

Recently I was investigating some strange problem at a customers site, where a nightly SQL Server 2005 batch job would slow down more and more as time went by. A restart would make it go fast again, which felt really strange and uncomfortable. Eventually after some time of investigation, it turned out that we had run in to this bug.

Adding the trace flag 8030 to the SQL Server fixed it!