I have a member who is unable to post to "groups"

I have a member (Kerry Hart) who can't post to groups. When I sign in as her, I try to comment in a group and click "Post Update."

The "Post Update" disappears once I click it and... nothing. Nothing happens. All my other users/members are able to post.

I troubleshooted the hell out of it and nothing worked. I finally completely deleted her account and all associated content. Then I re-added her. Same problem.

I then added a different member and called him "Sherlock Holmes." He was able to post without a problem. OK. I deleted Kerry's account (again) and then re-named Sherlock Holmes to "Kerry Hart" and edited the email address.

And now she's unable to post.

My mind is kind of boggled.