Some cases not being shown on contact Case tab selector

Some cases are missing from the Contact Case Tab selector altho they show up on tab count and can be seen from Find Cases. Apparently a problem w/ a limit clause in the query (see Eileen's comments below).

— original post (turned out to be case .xml file misconfig - no open case activity) ----
I don't fully understand when this stopped working on both a live site (4.1.5) and dev site (4.2.0)
Outcome is that after 'creating' a case and seeing the 'manage case' screen there is no Open Case Activity listed, and if the user then leaves that screen and then tries to find it on the Case Tab it does not show.