All you need to do is right-click on the Taskbar, select Toolbars and uncheck Touch keyboard. Simple as pie.
Has never come back for me.
Drugo, is this on a machine with a touch screen? I kind of expect that it would be persistent on a machine with a touchscreen.
As Adam says it's temperamental ... you need to set the Touch Keyboard and Handwriting Panel Service to manual.
As I said, I suspect this is probably only on a machine with a touchscreen, my non-touch laptop has no problem as long as I uncheck the the Touch keyboard from Toolbars.
Try the tutorial in the second post - you want to turn off the touch keyboard toolbar not the on-screen keyboard.