Problem in filing 2nd revised return online ???

Hello everyone,

i had filed original return of AY 13-14 in itr-1 of my client before due date.

i filed the revised return on 10th august 2013.

i noticed some mistake and want to revise the return again.

i filled the form correctly and entered ack no and date of return filed on 10th aug (1st revised return). but when i go to upload the form it showing as invalid acknowledgement number. what should i do to revise the return ?