The way solutions are handled within CRM 2011/2013 are that unmanaged solutions sit on top of any managed solutions. It's more than likely you have an unmanaged solution with the account entity included and the "Primary Contact" set as the label.
http://i.msdn.microsoft.com/dynimg/IC443916.png
Alternatively, this could be related to the UR you are presently on. Prior to UR12, this was an issue. To remedy, you can either create a brand new managed solution with this label change or update the roll-up. Unfortunately, incrementing an existing solution doesn't update labels appropriately (prior to UR 12).