HTML not working

I have installed HTMLArea for Drupal 5 and I got the Xinha 0.91 versions, compressed and uncompressed. I have tried both and htmlarea is not working. I can see the button images, but the area box isn't shaded and if I write something and press any button, it doesn't do anything. I am using firefox 1.5.0.6. I don't know if you need more info to understand if this is a bug or my error. I have tried the demo available from the project page and it works ok for me, so the problem must not be in my firefox. And well, as soon as htmlarea captures my textareas and places the images in them, I assume I configured things correctly. is there something I must do in order to have it working, like editing some file or renaming something? The help files and readmes don't say a word about it.