Purpose of an external oscillator in powering up?

[NorwegianFunk]

Hey guys
I started programming the PIC18F46K20 QFP this fall, but was using a development board (the starter kit for said pic) - but that being said, I want to learn more about the hardware interfaces and build my own custom design on a breadboard. So I just purchased a DIP version of the same pic, and just all the necessary components I feel I may need - but forgot about the xTal.
- and it won't start. MPLab (using the Pickit2) tells me there is a Vpp voltage error.

My question is: Do I need an external Xtal just to get the pic up and running?
Or is this another problem? I am noticing that the VDD pins on the pic, once connected to the breadboard, load down the 3.3V rail that I created. Same with the pickit. Am I shorting something somewhere? I will provide a schematic if anyone needs it, but for now I really just want to know if an xtal is necessary.
thanks!

 

[Diver300]

You have to let the PICkit change Vpp as it wants. It is normal to have a pull-up resistor on Vpp of about 10 kΩ.

It sounds like you have got Vpp connected directly to the power rails so that it can't be changed by the PICkit.

 

[NorwegianFunk]

Thanks, that pull-up resistor helped.
you know what also helped? I had the pickit wired up backwards!!!