hey, I'm running 10.2.4 on a pismo pb and so far i havent had any trouble with it ging to sleep. it could be that the webserver is preventing it from sleeping, like a background process. i know that when i run itunes and leave my comp on,the screen goes black after 7 mins(i set my screen to turn off after 7 mins, but to sleep after 10). so itunes prevents the pb from sleeping but lets the screen turnoff.
it also could be ur old prefs. i did a completely clean install of 10.2 and its been fine since then, even the battery menu in the dock works now. lol
let me know how u get on