We have recently had a user that has changed departments within the company and subsequently has changed OU.
Since then, the first log on attempt fails, but subsequent login works ok.
Error in log shows....
20/12/2012 08:35:52 Webserver: ADsOpenObject1(LDAP:company.com/CN=User Name,OU=Department,OU=Sub Department,OU=Employees,OU=Company,DC=company,DC=com): 80072030: There is no such object on the server
It appears to have cached the location on the user, OU=Department is wrong in the log.