MSNBC contains a wonderful interactive on fatility information from the war. You owe it to yourself to check it out.
I noticed only the following confirmed FATALITIES from friendly fire:
3/23: 2 British pilots killed when their Tornado is shot down by a Patriot. (This is also the day that a US Captain and Major were killed by a grenade thrown into the barracks - but this is NOT counted as friendly fire).
3/25: 2 British soldiers killed when 2 British Challenger tanks exchange fire.
Now, I realize this doesn't account for the 31 marines wounded in a firefight or other casualties that are not fatalities.