Have you seen this error message before:
"The parameter 'addresses' cannot be an empty string. Parameter name: addresses"
We get this when a user has been invited to join a second site collection on our extranet, when their email address already exists for another site collection. They get this error message when they click on the link provided by the system to register. I can send screen shots if that would help, but I wanted to check first to see if maybe you've seen this before and you have a quick answer. Thanks,
David from College Station
Hi again, it looks like we have solved this one by changing some registration settings. After we changed the bottom two to 'No' (for some reason we had them on 'Yes' even though the first one was on 'No'), everything worked fine:
This error occurs when one or more of your configured approvers does not have an e-mail address registered in their SharePoint profile. Can you confirm this fact? This error could also have been cleared up by removing the corrupt approver or disabling the approval option.