Yeah, the disable/enable trick works in XP and 2003, but not Vista.
For Vista, you'll have to actually delete the last icon (just to the Recycle Bin, not permanently), unlock and resize the bar so it's just slightly smaller than it should be to fit all of your desired icons, lock the taskbar again, and then undelete the last icon. The bar should expand just enough to fit your icons and leave no unsightly space.
Silly, but effective.