Are you sure you got your Permanent residency? Normally you get first your temporary residency, which will also get you a DNI, and then after 3 years your permanent one.. the "Precaria" has the same value as your DNI (at least that is what my lawyer told me), and is normally given to people applying for a residency and getting the paperwork approved, which doesn't necessarily mean that the application will be approved...Last week I obtained my Permanent Residency. They told me my D.N.I. should arrive in mail between 30-90 days.
Regarding obtaining the CUIL, I am not 100% sure if they will accept the "precaria"... I would guess that they want to see an approved application...