It's when the AI cheats. I seriously go berserk over that shit. I'm playing NBA Hangtime and once you hit the 4th quarter it's not uncommon to have the AI just go crazy. You try and dunk, they block you every time or run up behind you and push you over. You suddenly can't steal from them and your pushover doesn't work. They hit every single fucking three point shot. Meanwhile your AI buddy just turns into a total retard and just stands there and does nothing. I swear to christ, I got so pissed after getting raped in overtime that I was ready to fucking kill whoever designed that shit. The same thing happens in NBA Jam. College Slam still has the lame push-over move (no one clued Midway in on what fouls are), but at least it stays pretty fair.
Reminds me of some of the EA racing games with the rubber band gameplay. Drive a perfect lap? Too bad. Watch as your opponent suddenly appears right on your ass once you get near the finish line.