As I said before:
The plugin should be fine (note that it requires the legacy plugin enabled but this is mandatory since uddeIM requires the legacy plugin, too).
It provides some code so CB knows how to write into uddeIMs database.
So maybe it is a issue with CB which calls the plugin and J1.5. And if so, this is the wrong forum, but maybe Beat or Nant will see this post by chance.
Maybe it is an issue with the plugin and your J1.5 installation but without having a crystal ball nobody would be able to help without more information. The setup you have described seems to be ok. Are all access lists set correctly?
uddeIM & uddePF Development
CB Language Workgroup
CB 3rd Party Developer