Overflow when converting from 32768

Hello experts,

I had developed a ALV report program in SD module.

When I execute the program for 1 month period.. it is working fine. but when I select 2 months...am getting the short dump. that is pointing error in a standard FM. And the dump description is

Error analysis

An exception occurred that is explained in detail below.

The exception, which is assigned to class 'CX_SY_CONVERSION_OVERFLOW', was not

caught in

procedure "TSEG_READ_PRESTEP" "(FORM)", nor was it propagated by a RAISING

clause.

Since the caller of the procedure could not have anticipated that the

exception would occur, the current program is terminated.

The reason for the exception is:

When attempting to convert the value 32768, an overflow occurred.

My points are...

1. the program is correct. and showing correct data when we test for small data.

2. This dump is coming when I execute for 2 months or more..here the error showing is like syntax error....so I am getting confused whether it is syntax error or performance error.

Please suggest...

dk.