ubuntu 11.10

Not enough information to help you. If you are trying to edit an RTF file, then you may need to install OpenOffice/LibreOffice. If you are referring to something else, then please provide more relevant information.

Sounds like he's missing a dependency or some 3rd application that this 'power builder' app needs to use the 'rich text module'.

I think we could start with the exact package you are using "dpkg -l|grep 'power builder'" and then the eact error message from the log or screen.