DEFRAG!!
UI's are loaded at the very start, any time you see any thing it involves the UI. ( well not the patcher :P )
Fragmented drive is the cause of alto of the lag you get in-game after zoning and while zoning. IF you have under 2G of ram EQ2 will cache like ( OK I won't go there) but it cashes a lot with low ram systems. I've stated defragging once a week or more because it tones down some of the lag/choppy video for me.
Again I could be totally wrong about the caching but it helps me to defrag.