Being KO'D and Movement ending happen simultaneously. Go ahead and pick the order in which you choose to have them resolve.

hco always has you choose the square to drop off a carried person prior to making the attack, specifically prompting you where to place them should you loose hss.

after the attack you are then prompted to finish whatever movement you have remaining (if any) and then prompted for the official placement of the carried character

if that helps any

I choose the KO first and ending the movement second. Now there is no bizarro is on the map, so where do I place Lex?

Next to where bizarro was.

So now the issue isn't that it doesn't work, but that it can deliberately be made to allegedly not work?

I always thought (and I'm probably wrong) that you had to drop off a character being carried before you could make an attack anyway. So he would drop luthor in whatever square and then make the attack from that square, right?

In the case of Charge and Running Shot, this is correct. The movement portion of the power ends before the action to attack is given.

With Hypersonic Speed, however, the attack is made during the movement and before it ends. This can occasionally result in odd scenarios like this one, and in not being able to make an attack if a flight-less HSSer (Flash, Quicksilver, etc) enter hindering terrain. Once the movement ends, a HSS attack is no longer legal.