The MUI system can have new files added to provide extra or improved functionality. It sounds likely that you need to download extra MUI "classes" for these programs which dont work. They may be built upon the foundations of these classes.
Get snoopdos off aminet. It will be able to tell you which files your program is trying to load, where its trying to load them from, and if the loading failed. Just run snoopdos, then run jabberwocky. When you read the snoopdos log and it tells you which files it failed to load, go to aminet, and search for them.
Aminet link:
http://wuarchive.wustl.edu/pub/aminet/Go boy, go!!
