Sounds like a power supply problem or maybe something causing a short when the button is pushed.

The data sheet states when VDD drops to 4V a you have a brown-out.
Are both VDDs powered? Check the voltage on VDD when the button is pushed.

Two points to clarify.
Why the .1 cap to ground and not a pull-up of say 10k?
PORTA.7??? pin 7 is PORTA.5.