Steve and I were on, working and talking. We got a bug report that took over and hour to find. It was a random cart problem, but it wasn't introduced from the cart itself. We found that if someone had a cart going, and they just used the cart, no problem. However, if they had a cart going and then updated their personal settings and didn't have a default cart type, it could flip the cart type back to unknown or undefined. It only happened if you did a certain sequence, so we added some code to not flip it to unknown if no default cart types are specified. It sounds weird, but it took a while to figure out what was going on. One of those sequence things.

As a side note, this setting described above, is used on hundreds of other pages to control the checkout process for gram controls and invoicing. That made it a bit more challenging.