Unable to register new users

We have been running XWIKI for a couple of weeks now, and all had been running great. Earlier today, a new user registered for the site, having no problems. I added him to a group to enable him to edit content on the site. A little later, another new user attempted to register for the site, and he was unable to register. I looked in the Tomcat logs directory and found no errors. I also bounced the servlet and ultimately rebooted the box to see if something like that was the source of the problem. Nothing has enabled us to register new users. Each time we attempt to register a new user, I get the same response, "An error occured during the registration process. Please contact the support?", and the user is not registered. Trying to narrow down the problem, I started a separate instance of the servlet against the same MySQL database and encountered the same problem. When I ran the servlet against a test copy of the base xwiki mysql database, the problem is not found. This leads me to believe that the problem is within the database itself. Again, there are no errors within the tomcat logs directory log files. Any other suggestions? Thanks, Johnnie