I assume the .dll files are listed in help>About Installed Plug-ins? Inject PMD has not been updated to work with the current version of DS. Mimic and Keymate should - try redownloading and reinstalling. I suspect Fizz-X_Alpha was a trial version of implementing a physics engine, it's probably for an older version and I don't think it has been updated (and if it had it would hopefully be at least Beta by now).