Finally after almost 6 months since my Clase Ejecutiva/Business Class trip at Christmas and New Years with Grupo TACA, my problem has been acknowledged and solved! ^
This morning I received an email reply from a Manager at United Mileage Plus in Chicago whom acknowledged problems both with TA flights automatically posting to UA Mileage Plus as well as the IT problem they are also working on with LR-operated Grupo TACA flights flown in Business Class - the COS bonus doesn't post.
The manager replied in the best way I could reasonably expect. He posted the COS bonus I had expected when I booked this ticket back in October 2007 and gave me a "little extra" for the dozens of phone calls and emails I have sent about this issue since way back in late January.
I would be happy to forward this managers contact information to those MP members are still having problems with missing Grupo TACA flights. Just PM me.