programming fuck ups

What's the biggest screw up you ever made writing software?  Once a team I was on overshot a DCUT for some datacenter automation tools by two weeks, and it still ended up being shitty because the customer kept wanting to add shit.

Spent a whole week trying to figure out why my skeletal animation wasn't interpolating properly (flickering, looking like a lot of vertices get sucked into a black hole whose origin strangely didn't move with glTranslatef calls)... only to find out it was due to floating point errors and divide-by-zeros in a couple of my Quaternion member functions.

Whatever happened to programs terminating fatally with an exception when a divide-by-zero happens?  God damn, that pissed me off.