AJAX Register - once installed, can't access individual users through User Mgr

Hello all.

I just installed AJAX Register on a Joomla! 3.1.5 website (PHP 5.4.19).  After adding some extra fields and creating a test user with them, I can no longer access any individual user through Joomla's User Manager.  I can see the users, but get this error message when I click on them to edit or view the user info:

Error
String could not be parsed as XML

I've uninstalled other items I've tried (K2, Community Builder, etc) already.  I like the features of AJAX Register, but need to be able to access the users still!
Thanks!

Probably an error in the extra fields you added. Unpublish one by one to see which one causes error and then check the text in it. Special characters, quotes or similar are common cause of broken XML.

That did the trick. Thank you

Also, in case anyone is having the same issue, the system had no problems with "?", but what locked it up was the "&"...

Which field type was it and where did you have a "&"? In label, options, default value or?

It was a text field, and the "&" was in the label itself.