Emulators often do odd things with the texture buffer, so I'd get off of them for a sec and perhaps try a pc game that you know works.
The fact that the emu is slowing down when trying to load textures dynamically suggests a throttling issue, and by that I mean that you have low bandwidth to the "pipe" for your gpu somewhere. This can actually be a hardware issue. Improper voltage or a slow buss speed can do this. Again, it could be the video card drivers.