A required field called contenttypeid is missing or has an invalid value.

[WOLF-G4MIN-X]

I am working on a website of a friend of mine, and today we got the following issue:

A required field called contenttypeid is missing or has an invalid value.

When it happens:

So, you register an account, all fine. You get the email for activation, you click on the activation link, and that comes up.

So you see that error. Now you refresh the page, and it goes to the standard:

Your account has been activated, but you are currently in the moderation cue to be added to the forum.

That second part is how it should be from the start, when you click the activation link in the email. But it doesnt. It only comes up after you refresh that already clicked link.

Whats with that ?

I already checked the phrases for activateaccount, all is standard in there. Anyone know why this issue could be ? I already looked on Google, there were posts with similiar messages but not the same. So its a different issue i suppose.

Any help would be appreciated.

Wolf