Revenue posting to future period and not to open period

Generate Draft Revenue process is posting Revenue to Future period instead of an open period. We have the 13th period open and July set to pending close. Aug is future.

Revenue in that scenario generally posts to 13th period - however now the revenue is getting the effective date of 31-Aug-12 inspite of the the 13th period being open.

PA_GL Interface table shows the PA date as 31-Aug-12.  How can this be corrected ?. what might be the problem that is causing this and the revenue not posting to the correct open period.

Thanks