Trouble inviting new accounts to a group, error msg: “The following user(s) can’t join any more gruops: *** Email address is removed for privacy ***”

I have a group that my coworkers and I use for our job. We just hired several people, and I want to invite their hotmail accounts to our group. I have had some success in inviting people to the group, but I have reached a point where all of the hotmail accounts that I try to invite get the error message of ""The following user(s) can't join any more groups: *** Email address is removed for privacy ***" This doesn't make sense because they are not part of *any* groups! How do I get them into the group?

'version' of skydrive: Skydrive on the web
Browsers: Internet Explorer 10, Firefox 23.0.1
Operating System: Windows 7 enterprise
3 different computers (all windows) and 3 different accounts
I have cleared my cache/cookies and tried to access the group again, still no luck
Skydrive status: "Running normally"; "Account, Outlook, People, Calendar, Skydrive, Connected Services, Messenger, Family Safety" .... all running normally

I also tried accessing it on my mobile device samsung galaxy S3, using both the internet app and the skydrive app, neither of which I could get access to groups.

I have tried promoting other accounts to co-owner status, and then inviting new accounts via the co-owner account, but I still get the same message.