Error while using AIR 2.7 in Mobile applicaton

hi,

when i am trying to use AIR2.7 in Flex mobile project, it shows the error.

Process terminated unexpectedly.
invalid application descriptor: Unknown namespace: http://ns.adobe.com/air/application/2.7

Launch command details:  "C:\Program Files (x86)\Adobe\Adobe Flash Builder 4.5\sdks\4.5.1\bin\adl.exe" -runtime "C:\Program Files (x86)\Adobe\Adobe Flash Builder 4.5\sdks\4.5.1\runtimes\air\win" -profile mobileDevice -screensize 600x986:600x1024 -XscreenDPI 168 -XversionPlatform AND D:\WSFlexPremium4.5\VCCheckMobile\bin-debug\VCCheckMobile-app.xml D:\WSFlexPremium4.5\VCCheckMobile\bin-debug

AIR 2.7 is important for me because i want to use 'Echo Cancellation' feature in Mobile.

i tried all things, now i giveup.

Please help me out

best regards,

Vishal Sood