CostCo, Sam's or BJs, if they have them in stock. Mine didn't.
You can buy direct from an Interstate store if you have them locally.
I bought mine from Autozone with an online coupon and ended up saving about 25%.
Your high speed network was down. Immobilizer com between CEM and ECM was not possible and stater will operate but the immo function stops ECM when no security code is sent from CEM. The anti-skid message is a default DIM message when the Brake Control Module communication is lost. Could be low voltage, could be something else. Full code readout will let you know.
Or you put new battery in it and see if it does it again.
+1 on the battery. Happened to me with both of my '04 Rs that had the original Volvo batteries. Slightly different symptoms.. one car died completely while the other went into limp mode. Replaced batteries with Interstate brand and both cars were good as new.