I just opened up one of my sites to membership. I've sent email invitations to a number of people. Some people have joined with no issues (both members and non-members of Wikidot before the invitation). However, one individual has not been able to join. I'm trying to get a description of what happened or didn't happen, but the person is quite busy running around the world, so it's hard to get a clear description. But, when I try to send a reminder to join, I get a rather generic error message: "Error! An error occurred while processing the request." In fact, this same error message occurs with other invitees, as well. Does anyone have a clue what's happening and how to fix this issue? Is there a way to just add members without going through the invitation process?