What instruments are having the problem? Which version of the GPO library are you using. Make sure you have the latest because there was a version out there that had issues such as this.
Now that you mention it, I believe that I have had the problem only with horns.
I don't know which version of the GPO library I have. How do I find the version number? If I have an older version, is there a free upgrade on the Garritan website? I bought it only about a month or so ago.