I've not seen a delete cache option in PalmReader, only in the web browser. Tap near the top of the screen when in Palm Reader to bring up its menus (all Palm apps work that way).
There are two versions of Palm Reader and Palm Reader Pro. However the free version has plenty of features. You might want to download the latest version from www.palmdigitalmedia.com. You'll probably also find support for the app there, since they're the ones that make it rather than PalmOne.
-------------------- Lisa Gade Editor in Chief, MobileTechReview