If you set a breakpoint on an address in the debugger, it will automatically break whenever the game tries to access the address.  This makes debugging a lot easier.  However, it primarily does this for "lw" and "sw" instructions.

I've been adding it various places, like here, so that I can see when HLE is writing to memory also.

In this case, I had set a breakpoint on a replacement function which was not supposed to be a replacement function.  Where was it being modified?  Was the game somehow adjusting it without properly loading a module?  When I added this function above, I was able to see it was US modifying it, and so dug deeper.

-[Unknown]