I have created a Cordova 2.1.0 app, It ran fine for the first 2-3 times. But now when I am trying to run it through terminal it is giving me the following error.I didn't change anything.

Ankurs-Mac-mini:~ ankur$ /Users/ankur/Desktop/CordovaSMS/cordova/emulate 
Ankurs-Mac-mini:~ ankur$ 2012-10-17 16:11:08.695 ios-sim[7032:507] stderrPath: 
/Users/ankur/Desktop/CordovaSMS/cordova/console.log
2012-10-17 16:11:08.698 ios-sim[7032:507] stdoutPath: 
/Users/ankur/Desktop/CordovaSMS/cordova/console.log
[DEBUG] Session could not be started: Error Domain=DTiPhoneSimulatorErrorDomain 
Code=1 "iOS Simulator failed to install the application." UserInfo=0x7fc643902320 
{NSLocalizedDescription=iOS Simulator failed to install the application.,
DTiPhoneSimulatorUnderlyingErrorCodeKey=-1}

any help would be appreciated. Thanks