UI--> Looks like 2 guys were talking about the UI causing issues. Specifically it running checks for mouse input(Alt key) when the mouse wasnt even activated and it(Scaleform) generating shaders that seemed uneeded.
Packets--> They are creating a packet profiler that is basically looking at how you are receiving data. The network is probably the biggest thing causing PS2 to be a single threaded process as you are waiting for updates on the actions of possibly hundreds of entities many times a second.
Cache & Multicore --> Cache hit/miss is how well the code is optimized so that instructions will operate on data stored in your CPU cache rather than having a cache miss, which means that the memory page was not loaded in cache and you then have to pull the data from memory or god forbid secondary storage. This is why you get really good performance from SSD's and RAMDriving games like Planetside where suddenly a Galaxy appears and the game has to pull a texture from your hdd and push it to your GFX card. You get frame rate loss and you get game update delays. The multicore enhancements were just referring to how much stuff they can make your other cores do in parallel without being bottlenecked by the gameloop sequence. For instance you cant really very much sound stuff in parallel because you need to know from the game loop that someone fired a gun that created the sound.
Like the director said, its really hard to find time to break the bone and reset it when its a continuous game.