Thanks Dimmy, this is exactly the kind of help I need!
I have tested ppp in many ways, but two things make it hard for me to find errors before they happens:
1. I’m a php and sql newbie

2. My experience in MODx is also still very limited and I don’t know what to test for!
So to make the code better I really need feedback from testers, so again, thank you for the help.
And for the problems in your posts above:
I had no idea that there would be occasions where only table web_users are used alone, without also adding a post in web_user_attributes. If there isn’t a corresponding row in attributes sure it will generate an error as in your first post. And also it would make ppp to select the wrong user under certain circumstances.
I have used internalKey when putting info into the database, but not when retrieving. Stupid error!
Both these errors would not affect most users, but the internalKey stuff I’ll fix asap as it’s such an easy fix.
I’ll also add some logic to check if user exist in attributes table before trying to fetch data.
Sorry to say, I’ve already spent way over 500 hundred hours in making ppp (including reading php, sql and MODx manuals

) and at this moment my time is more limited as I have several web site projects going on. But when someone finds any problem I sure try to fix them, and perhaps also add some new features on request.
Again Dimmy, I thank you for finding out these problems! And if you find time to do some bugtesting that’s even better!
To Other ppp-users:
If I understood the above problems correctly, these problems wouldn’t occur for the majority of users. If you’re using customized ways of adding users instead of the "built in" that comes with MODx default, you could ran into trouble.
And lastly, as always: PPP is under development status, problems will occur.