I have been able to clear them, but only during a re-install of the OS or of App World. App World also takes a while to get the newest version of the apps I have installed, for instance Slacker. Slacker is only on version 2.0.12 on App World and I have version 2.0.49 installed. When I updated Slacker, App World thinks I have un-installed it. I get around that by going into App World after installing the newest version of the program, in this case Slacker, then selecting re-install. As soon as the Blackberry prompts me to overwrite the existing version, I cancel the installation. App World now knows that I have Slacker installed and has the correct version information on my phone.