System is adding to the view filter criteria

This is in CRM 2011 RU13. The following is happening on a custom entity:

1. Create a new view, the filter criteria is automatically set to the following:

(Group And) Status = Active, Suppress does not equal yes
(Group And) Status = Active, Suppress does not equal yes, End Date does not contain data

If I delete the second and group, click OK and then go back to the Filter Criteria it comes back and adds the following:
Status Equals Active, Suppress Does Not Equal Yes

2. If I edit an existing view the same behaviour occurs.

This is starting to drive me around the bend! - What am I missing???

One point to note, please do not suggest moving to a later rollup as this is not possible, the client has strict rules about applying updates and everything goes through a change control board so an update isn't going to happen anytime soon.