problem in retro payroll

Hi Experts,

I have a problem in payroll,

when i run payroll for march month ,it is running for last 4 periods ,means december to march,

actuevally there is no change is master data,

if i am trying to set earliest retro date as 01.03.2009 in infotype 3 ,

payroll is not running it is saying

" Retroactive accounting dat set by system, 01.10.2008, is before pers. EARLI"

pls help me.