Basically the symptoms are that the LJ icon dissapears under XP.. Personally, this should be noted in support also, that if the user is running XP, this should be the FIRST THING that they check. Why have the user go thru their registry unneccacarily? The icon can be found by clicking on the > symbol on the taskbar also... but what i am suggesting is a perm way to make sure the lj icon is ALWAYS visable.
Basically here's the fix.
Right click on the system tray, choose properties. under the taskbar tab, on the bottom, they'll be a checkbox that says "Hide Inactive Icons"... unchecking that would fix it also. but the way to keep this checked, and still have the LJ icon active, would be to click customize right next to it, and then finding LiveJournal in the list and choosing "Always Show"..
Here's a screenshot
You'll see the steps needed.