The FMS logs show the following error:
2015-02-11 13:28:28.902 WARN [http-0.0.0.0-8080-4] com.quest.nitro.service.security.auth.spi.NitroExtendedLdapLoginModule - Failed to search associated group for user <Username>
javax.naming.NamingException: [LDAP: error code 1 - 000020D6: SvcErr: DSID-03100754, problem 5012 (DIR_ERROR), data 0
remaining name 'CN=Group/Name,OU=Groups,DC=contoso,DC=com'
When LDAP is configured to use the "Direct" group search method, the search will fail if the user is a member of a group in AD that contains a / in the name. Please note that this group does not have to be imported into, or visible within FMS for this to affect the user.