It occured to me some time ago that French and Portuguese - unquestionably Europe's sexiest-sounding languages - are also the only ones on that continent that happen to be heavily nasal. The odds of that being a random coincidence can't be very high.
If James Cameron wanted his Avatar aliens to sound sexy, he should have told his linguist to make their fake language outlandishly, freakishly nasal - like French on viagra. Which reminds me: the Russian word for blue (goluboy) also means gay. Avatar must have produced so many chuckles in the former USSR.