I am using a 16F88 in a circuit and my header is this:

OSCCON = $60 'set int osc to 4mhz
ANSEL = 0 'SELECT ANALOG INPUTS 0 = NONE AND ALL DIGITAL
ADCON0 = 0 'AD MODULE OFF & CONSUMES NO CURRENT
CMCON = 7 'COMPARATORS OFF

The PIC behaves perfectly.