"I've connected power, then RST to +5v and Xtal1 and Xtal2 to a crystal, and 33pf Caps."

In order for the AT89C52 to operate RST must be logic 0. Per the ATMEL AT89C52 Datasheet RST high for 2 clock periods RESETS the device.

The suggested RC network allows the 89C52 to delay starting up until power has stabilized.

Hal