If your old call studio application used to work fine and even the simplest of applications don't seem to run in the Cisco unified call studio 9.0 debugger then you may need a mail.jar file.
This the error you must be getting every time
Prompt: I'm sorry, there was a problem with this application. Please call back later. Thank you. (/CVP/audio/error.wav)
The actual error which could give you a hit what may be happening is in this file startup_error_logYYYY-MM-DD.txt in this folder C:\Cisco\CallStudio\eclipse\plugins\com.audiumcorp.studio.debug.runtime_9.0.1-SNAPSHOT\AUDIUM_HOME\logs
SERVER ERROR: There was a problem loading classes from CVP_HOME\VXMLServer/common. The error was: There was a problem loading classes from CVP_HOME\VXMLServer/common. The root cause was: java.lang.NoClassDefFoundError: javax/mail/Authenticator
To fix this go to http://www.oracle.com/technetwork/java/index-138643.html download the latest Javamail.
Extract the contents and in the directory(javamail-1.4.x) you find a file called mail.jar.
Copy that mail.jar file to C:\Cisco\CallStudio\eclipse\plugins\com.audiumcorp.studio.debug.runtime_9.0.1-SNAPSHOT\CATALINA_HOME\webapps\CVP\WEB-INF\lib
Re-run your application. That should fix it!
Credit goes to http://developer.cisco.com/web/cvp/forums/-/message_boards/message/17876067