I'm using a 16F676. The program was working fine till I changed the hardware to use PORTA.3 as a digital input to recognize a pushbutton. Now as soon as the button is pressed the whole thing locks up and I have to turn the power off to get it to reset.

I know I need to turn MCLRE off. I think I did that, but obviously I did something wrong or I've left something out. Please help me figure out how to use PORTA.3 as a digital input.

FYI, PORTA.1/AN1 and PORTA.2/AN2 are connected to potentiometers and being used as analog inputs.

Code:
#config 
    __CONFIG _CP_OFF & _PWRTE_ON & _INTRC_OSC_NOCLKOUT& _MCLRE_OFF
#endconfig


ADCON1 = %00000000
ANSEL = %00000110
CMCON = %00000111      


TRISA = %00001111
TRISC = %00000000


' Set TMR0 to interrupt every 16.384 milliseconds
   OPTION_REG = %10000101        ' Set TMR0 configuration and enable PORTB pullups
   INTCON = %10100000           ' Enable TMR0 interrupts
   On Interrupt Goto tickint
    
    '                      
    '    Hardware connection
    '    ===================
 
    CS          VAR PORTA.5                                                                     ' digital potentiometer SPI connection
    SCK         VAR PORTC.2                                                                    ' digital potentiometer SPI connection
    SDI          VAR PORTC.1                                                                    ' digital potentiometer SPI connection
    tempobutton var PORTA.0                                                                  ' push button 1
    tempoLED var PORTC.0                                                                      ' push button 1 status LED
    trailsbutton var PORTA.3                                                                    ' push button 2
    trailsLED var PORTC.4                                                                       ' push button 2 status LED
    mosA var PORTC.5                                                                           ' MOSFET switch A
    mosB var PORTA.4                                                                           ' MOSFET switch B
    mosC var PORTC.3                                                                           ' MSOFET switch C