Navigational software glitch forces Lockheed Martin F-22 Raptors back to Hawaii
....seems it was MUCH more than merely the 'navigation' system that failed -- the fortunate presence of good VMC weather (.. and the tankers) may have prevented loss of all aircraft.
Apparently the pilots lost all attitude-reference for safe IMC flight/landing, as well as significant loss of fuel-system controls and communications.
http://www.dailytech.com/article.aspx?newsid=6225