You're talking about the Percussion Strip, right? And the UI is blank?
Could be some resource files have been deleted, like the bitmaps that are used to draw the controls. Look in the vstplugins\percussion strip\resources folder. There should be a whole mess of .bmp files in there, plus a couple .cwres files. The cwres files are text files that link the bitmaps to their respective functions.
If that folder's empty or missing, you should be able to re-install just that plugin from the installation disks.