I went to migraciones today to renew my visa rentista. I had the same papers as last year, along with a translation of my new passport. It wasn't quite enough. This year they are asking for a new (less than six months old) certificado de antecedentes penales en argentina. They did not ask for it when I renewed last year.
It is possible to get a form on line and pay at any branch of the banco nacion. The fees vary slightly on how fast you want to pick up the certificates (8 hours, 24 hours, or 5 days) after submitting the form and providing fingerprints. There doesn't seem to be an eight hour service, so 24 hour service is what you'll get.
http://www.dnrec.jus.gov.ar/TramPerWeb/inicio.aspx
The on line information indicates that you can then "apply for" and obtain the certificado at one of the centros de gestacion publico (CGP). When I went to the CGP location closest to my apartment, they gave me a list with four locations, including Cabildo 3067 that actually issue the certificados. I also spoke with a man at migraciones who told me he obtained his certifacado at Piedras 115 (near Av 25 de Mayo.), but it isn't on the list. I'll go to the Cabildo office tomorrow and add more information as soon as I have it.