Friendly fire incidents are somewhat normal for troops in combat. Shit happens. But this incomplete list seems to show two distinct issues. "Western" troops getting killed by Afghan police and military personal in direct confrontation over personal issues while Afghan security personal is getting killed in botched air attacks.
Personal honor issues versus careless brute force application. A difference?
Afghan soldier kills Italian counterpart in Badghis, Jan 19 2011
U.S. marine kills Afghan policeman after dispute, Jan 15 2011
Three Afghan police killed in Nato air strike, Jan 10 2011
NATO air strike kills 4 Afghan soldiers: ministry, Dec 16 2010
Another ‘Afghan Army Soldier’ Kills ISAF Troops, Dec 7 2010
Afghan Policeman Kills 6 NATO Troops, Nov 29 2010
US soldier kills Afghan policeman, Nov 11 2010
Afghan soldier turns weapon on American troops, kills 2, Nov 6 2010
Afghan policeman kills two Spanish trainers and interpreter, Aug 25 2010
4 Afghan Police Killed, 13 Wounded in ISAF Air-Strikes, Aug 22 2010
Afghan soldier kills two US civilian trainers, July 20 2010
Rogue Afghan soldier kills three British Gurkhas, Jul 13 2010
Five Afghan soldiers killed in botched NATO airstrike, Jul 7 2010
6 Afghan soldiers killed by German friendly fire, Apr 03 2010
Swedish soldiers killed by 'Afghan police', Feb 8 2010
Anger as NATO airstrike kills 4 Afghan soldiers, Jan 30 2010
U.S. soldier killed, 2 Italians injured when Afghan soldier opens fire at military base, Dec 20 2009
Afghan policeman kills four colleagues: official. Nov 29 2009
Rogue Afghan policeman kills five British troops, Nov 5 2009
Afghani cop shoots, kills American soldiers during patrol, then flees, Oct 3 2009
Afghan soldier kills two coalition troops, U.S. says, Mar 27 2009
Coalition air strike kills nine Afghan soldiers, Oct 23 2008
Afghan policeman kills a US soldier, wounds 3, Sep 29 2008
Foreign airstrike kills 9 Afghan police, Jul 27 2008
Air Strike Reportedly Kills Afghan Police By Mistake, July 20 2008
Afghan Police Killed By Us Troops in Mistake for Taliban, Jun 13 2007
Afghan soldier kills 2 U.S. troops outside top-security prison, May 6 2007
Marine embassy guards mistake Afghan soldiers as assailants, kill four, May 21 2003
How the U.S. Killed the Wrong Afghans, Feb 06 2002