Surely, a navigation failure of this kind would require a Pan Pan call as neither the aircraft, its occupants nor anyone else is in 'immediate need of assistance'.
If you are in a radar environment then it is now the controllers job to take whatever action he deems necessary but you should still be able to navigate using VOR/DME. Also, I'm pretty sure RVSM compliance is not dependant on nav input but I'm prepared to be corrected...
However, if you are out of ground navaid and radar coverage and you are lost then 'Mayday' would be appropriate.
BTW 77, I'm a little confused about your scenario 'Malaysian airspace over India' - last time I looked Indian and Malaysian airspace were not even adjacent.....
1106
Last edited by Type1106; 16th Aug 2010 at 15:43.
Reason: Grammar