PM extension

I've installed the PM extension, but I can't get it to send messages. When I try to send a test message in the PM-writer, I receive this error: "This member was not found or has disabled private messages." The recipient text fields autocompletes member names, so it has access to the members list. When I disable PMs for a member, his name no longer appears in the "autocompletion" list, so that seems to work just fine. But when the send button is hit, the above error message shows up no matter what I try.

I've found little documentation about the PM extension. Does anyone know how to make it work? I'm running Typolight 2.7.6

Thanks,
Bart.

Here's a little update:
The PM-system works in some directions. Some members can send PM's to eachother. Other members can't initiate new messages, but answering to a received message seems to work for everyone.

I really need to get this to work. I'm receiving opposition from a member that claims this kind of functionality works out of the box with Drupal. But I've invested a lot of time in learning my way around in Typolight and I'm not prepared to trough the towel so easily. Besides that, I like Typolight a lot. I would appreciate a little support though.

Best regards,
Bart.