Hi MICDI,
Are you using Pro Tools 8.0.3 or 8.0.4? If so, there is a known issue where if you use another AudioSuite plug-in prior to using Pitch 'n Time Pro in the same session the output is silence or pops as you have described (see here ->
www.serato.com). For now the workaround is to ensure Pitch 'n Time Pro is the first AudioSuite plug-in used or to restart Pro Tools.
We are currently working on a fix for this for a future release of Pitch 'n Time Pro.