I had the same problem.
Also, I all ready have plugins in folder, but plugin installer seems to be from version 4. Installer all ready has a .dat file, but am I supposed to create one myself?
Yes, just use Notepad.

Copy/Paste into folder Ultra Hal Assistant 6 and still get version 4 error.
Brain tab only has advertisements for plugins.
I all ready have plugins in the folder by default, but cannot see any .uhp files through the program.
I've read where version 6.xx does not support on-the-fly plugins, but I thought that was what the PluginInstaller was for...?
Does the default brain have some sort of protection where one has to create one's own brain first and then you see brains in brain tab (version 6 it's an avatar)?
Some Brain Editor buttons are grayed out, so that's another reason why I'm thinking that maybe one cannot modify the default brain...

This is like knowing how to give the car a tune-up but not knowing how to drive the thing.
- or do I need a first line of code/header for the PluginInstaller to work in version 6.xx?
I'm only guessing...