Try going to START>RUN (or hold the Windows Key and type "R") and type the following:
%appdata%
Hit ok and a folder will open. From there go to Cakewalk\SONAR X2 Producer. Rename the file "aud.ini" and "cakewalk.ini" to something new, like "aud.ini_Original".
Then restart SONAR and see if that helps.