1. Did a check on /public_html/app/etc/local.xml
<admin>
    <routers>
        <adminhtml>
            <args>
                <frontName><![CDATA[admin]]></frontName>
            </args>
        </adminhtml>
    </routers>
</admin>

2. Cleared var/session and var/cache.
3. Access with and without index.php
4. I ran the following SQL code.
SET FOREIGN_KEY_CHECKS=0; UPDATE core_store SET store_id = 0 WHERE code=’admin’;
UPDATE core_store_group SET group_id = 0 WHERE name=’Default’;
UPDATE core_website SET website_id = 0 WHERE code=’admin’;
UPDATE customer_group SET customer_group_id = 0 WHERE customer_group_code=’NOT LOGGED IN’;
SET FOREIGN_KEY_CHECKS=1;

SQL returns the following error code.
#1054 - Unknown column '’admin’' in 'where clause'

5. Ran with the following SQL Code again due to suspected punctuation marks
SET FOREIGN_KEY_CHECKS=0; UPDATE core_store SET store_id = 0 WHERE code='admin';
UPDATE core_store_group SET group_id = 0 WHERE name='Default';
UPDATE core_website SET website_id = 0 WHERE code='admin';
UPDATE customer_group SET customer_group_id = 0 WHERE customer_group_code='NOT LOGGED IN';
SET FOREIGN_KEY_CHECKS=1;

Results:
# MySQL returned an empty result set (i.e. zero rows).