AIX: ulimit gets halved when switching to bash from ksh

[ptgasior]

Configuration Information [Automatically generated, do not change]:
Machine: powerpc
OS: aix5.1
Compiler: xlc
Compilation
CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='powerpc' -DCONF_OSTYPE='aix5.1'
 -DCONF_MACHTYPE='powerpc-ibm-aix5.1' -DCONF_VENDOR='ibm' -DLOCALEDIR='/op
t/freeware/share/locale' -DPACKAGE='bash' -DSHELL -DHAVE_CONFIG_H  -I.  -I
 -I./include -I./lib  -I/opt/freeware/include -O2
uname output: AIX es2p180p 2 5 00CE9D2F4C00
Machine Type: powerpc-ibm-aix5.1

Bash Version: 3.0
Patch Level: 16
Release Status: release

Description:
        [Detailed description of the problem, suggestion, or complaint.]
                Logged in as default shell of ksh, then type bash.  Ulimit 
filesize
becomes half of what it was when the filesize isn't set to unlimited.
--- wily@es2a237q:/home/wily ---
$ echo $SHELL
/usr/bin/ksh
--- wily@es2a237q:/home/wily ---
$ ulimit -a
time(seconds)        unlimited
file(blocks)         2097151
data(kbytes)         131072
stack(kbytes)        32768
memory(kbytes)       32768
coredump(blocks)     2097151
nofiles(descriptors) 2000
--- wily@es2a237q:/home/wily ---
--- wily@es2a237q:/home/wily ---
$ bash
--- @es2a237q:/home/wily ---
$ echo $SHELL
/usr/bin/ksh
--- @es2a237q:/home/wily ---
$ ulimit -a
core file size        (blocks, -c) 1048575
data seg size         (kbytes, -d) 131072
file size             (blocks, -f) 1048575
max memory size       (kbytes, -m) 32768
open files                    (-n) 2000
pipe size          (512 bytes, -p) 64
stack size            (kbytes, -s) 32768
cpu time             (seconds, -t) unlimited
max user processes            (-u) 1024
virtual memory        (kbytes, -v) unlimited
--- @es2a237q:/home/wily ---
$

Repeat-By:
        [Describe the sequence of events that causes the problem
        to occur.]
See above.
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