clarifications needed on postgres/perl

Hi!,
we are using postgresql(6.3.2-10) on red-hat linux 5.2.
 we use perl-5 to access postgres.
 the problem we have is :
 we have a table having 13 fields, now when updating one of the fields
 from the perl program, for more than 800 records, the following error
is
 reported :
     "FATAL 1: palloc failed: memory exhausted."
 how ever when doing the same directly in psql monitor, there is no
 error. also when the number of records to be updated are below 800
there
 is no error.

 We also changed the buffer size to 256, still we get an error like:

        IpcMemoryCreate: memKey=155356396 , size=760632 ,
        permission=384IpcMemoryCreate: shmget(..., create, ...)
        failed: Invalid argument

        i know I have to build IPC support into the Linux kernel. i
        will have to rebuild the kernel and switch on this option.

 can u please tell me how to do it.?

 kindly suggest some remidies,
 we will be very thankful.

 looking forward to ur valuable suggestions very soon,
 with best regards,
 Team srishti.