Strangely behaving 16F877a

[financecatalyst]

Hi
I am using an external oscillator 4MHz. My program simply toggles one pin every 30ms.
Problem is that I see sometimes the toggling if I touch the PIC,leg of the capacitor (earth) or touch the bench the circuit is left on and sometimes it works fine and sometimes the led is just on constantly.

What could be the reason for this???