This is sometimes caused by ESRI still having a lock on the version since ArcMap is still open and we've released everything we can.
When this happens we've usually "marked" the version for deletion in the Px tables so that running the Orphaned Version Cleanup Tool in ArcCatalog (after closing ArcMap) should finally delete that version.
Give it a try and see if that helps.
1. Close ArcMap that posted the design (you are posting from ArcMap right?)
2. Open ArcCatalog, double click on your connection to the database to connect making sure to log in as SDE user or the owner of the offending version.
3. Right click on your connection and choose Orphaned Versions Cleanup Tool.