No match is found for contact when performing an e-mail search to add a contact to a Group with CiviCRM

In CiviCRM Manage Groups (home/civicrm/group) if you select a group and "Show Group Members", there is a feature to use a search engine to " Find Members of this Group".
If you enter one of the group member's e-mail addresses into the "Name or email" field and so a Search, you will get the message, " [Group Name] has no members which match your search criteria. You can add members here." This does not occur if you search on the user's First or Last name instead.

Steps
1. Access CiviCRM: http://civicrm.civicspacelabs.com/home/civicrm
2. Manage Groups
3. Select a Group and click "Show Group Members" (If no group exists, create one, add users and then go to Step #4)
4. Type one of the e-mail addresses for a member who belongs to the group into the field, "Name or email" in "Find Members of this Group".
5. Search.

Results
6. You will receive the message, "[Group Name] has no members which match your search critera. You can add members here."

Notes
1. Type the First name of the same user whose e-mail address you entered into "Name or email" and search again.
This time the group member will be found.