Hmmm....I wonder if you have too much capacitance (30uF). The large inrush current when you first turn on power together with stray inductances and whatnot may have caused a voltage spike at the input to the 3.3V regulator. I'm not going to defend this theory too much as it does sound fairly improbable, but I have read app notes on switching regulators that mention this phenomenon (ceramic capacitors are *too* good at their input and electrolytics/tantalum are recommended).
A-ha...here it is:http://cds.linear.com/docs/Datasheet/3411afb.pdf
Check out page 12, the section titled "Ceramic Input and Output Capacitors". I quote:
However, care must be taken when ceramic capacitors are
used at the input and the output. When a ceramic capacitor
is used at the input and the power is supplied by a wall
adapter through long wires, a load step at the output can
induce ringing at the input, VIN. At best, this ringing can
couple to the output and be mistaken as loop instability. At
worst, a sudden inrush of current through the long wires
can potentially cause a voltage spike at VIN, large enough
to damage the part.
You don't have long wires, but.....who knows.
I'm still betting on ESD. There may well be more rugged linear regulators out there but there are other components on the board that are equally susceptible. I would suggest developing better ESD practices rather than finding more rugged components
The MegaRAM shield
: add 128 kilobytes of external RAM to your Arduino Mega/Mega2560