Paul,

50 msec is too short, most supervisory chips assert Reset for 250 msec. This due to power supply bounce,etc. If you insist on using RC w/ Schmitt trigger, increase the time constant. But RC circuit will no take care of brown-out type conditions. The RC circuit does not handle this type of condition well.
Also if the power is interrupted for a time period less than the falling RC time constant, it will not Reset the uprocessor and you get all kinds of "funky" behavior.


Jacob