Unanswered question

I have the NL-REDIRECT-03 error which warns Unable to perform redirect,the previous request did not perform a redirection.It occurs in the login page only..I am receiving the 302 redirect for 1,5 and 10 users and no error for these users,,if the user request exceeds 50 users i am receiving that particular error ,,whats the problm..waiting for the answer,,