PIC16F877 Weird behavior

Hi guys,
I am experiencing a weird behavior of the pic16F877.

I have 24 led(s) That I have distributed on port D, C, E, and A.

I wrote a code were the first 12 Leds will trun ON, and after every PAUSE 500, A LED will trun off and another LED will trun ON from the second set of 12 LEDs.
Everything went well except 1 LED didn't turn ON at all. (I checked to see if it is burnt, but it is not). The LED was on PORTA.4

Then I wrote another code, where all 24 LEDs will turn ON, and They will turn off, one at a time.

I had a weird behavior: 6 LEDS didn't work and they are at PORTA.2, .3, .4, .5, PORTE.0, .2

Have anyone experienced this behavior?
Please if you have any advice or answer I will appreciate it.
Thanks