New test:

Code:
REFCON0=0
REFCON1=0
ADCON1=0
ADCON2=0
ANSEL =0           
ANSELH=0
CM1CON0=0
CM2CON0=0
SRCON0=0
SRCON1=0
WPUA=0
WPUB=0

TRISC = 0
PORTC = 0

ProgStart:
   PORTC = 0
   pause 1000
   PORTC = 255
   pause 1000
   goto ProgStart
PORTC.3, C.6 and C.7 work, PORTC.0, C.1, C.2. C4 and C.5 don't...
So... what's the common factor?