Okay, I should have expressed my question more clearly: "Is there any DOM processing going on when loading the MochiKit script files are loaded?"
I've tested the page without loading the MochiKit files and the sluggishness and the FF error message persists - so it's not MochiKits fault. Now I'm implementing a JS class that does record pagination by getting a number of rows via loadJSONDoc and displaying them it with the DOM functions.
