Collective order missing start date and finish date

Hi

I meet one problem for collective order. sub production order is missing start date and finish date.

and get error message is the date 00.00.0000 is not convertible.

when go into the sub production order then appears:

ShrtText
    Error in ABAP statement when processing an internal table.

What happened?
    Error in ABAP application program.

    The current ABAP program "SAPLCONB" had to be terminated because one of the
    statements could not be executed.

    This is probably due to an error in the ABAP program.

I want to know who ever meet such one problems and how to fix it.

Thanks very much

Sunny