Here is some very simple example code that exhibits a problem I am unable to explain.
The following code WORKS. Following it, I will show something that does NOT WORK.

@ DEVICE pic16F676, INTRC_OSC_NOCLKOUT
@ DEVICE pic16F676, WDT_OFF
@ DEVICE pic16F676, PWRT_OFF
@ DEVICE pic16F676, MCLR_OFF
CMCON = %00000111
ANSEL = %00000000
TRISC = %000000

PAUSE 1

Main:
HIGH PORTC.0
HIGH PORTC.1
HIGH PORTC.2
HIGH PORTC.3
HIGH PORTC.4
HIGH PORTC.5
PAUSE 500
LOW PORTC.0
LOW PORTC.1
LOW PORTC.2
LOW PORTC.3
LOW PORTC.4
LOW PORTC.5
PAUSE 500
GOTO MAIN

Now, If I replace the Main section with:

Main:
PORTC = %111111
PAUSE 500
PORTC = %000000
PAUSE 500
GOTO MAIN

It hiccups. Will blink once or twice.. maybe several times.. but will hiccup and stop and start very intermittently. What am I doing incorrectly here?