Input 00005XXXXX is invalid

Hi,

I am creating a web dynpro component. I have a context node T_BSEG of type BSEG to enter the line item data but when I try to enter the G/L account on the screen as '5XXXXX' I am getting the error "Input 00005XXXXX is invalid. Use the input help" I tried to select the G/L account from the input help but then also I am getting the same error. The G/L account is of type HKONT.

Any help is appreciated.