pwd as first command changes script behavior

[Quiring, Sam]

Configuration Information [Automatically generated, do not change]: Machine: 
x86_64 OS: linux-gnu Compiler: gcc Compilation
CFLAGS: -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' -DCONF_OSTYPE='linux-gnu' 
-DCONF_MACHTYPE='x86_64-pc-linux-gnu'
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL 
-DHAVE_CONFIG_H -I.  -I../bash -I../bash/include
-I../bash/lib -g -O2 -Wall uname output: Linux pdx-squiri-u2tb 
2.6.32-30-generic #59-Ubuntu SMP Tue Mar 1 21:30:46 UTC 2011
x86_64 GNU/Linux Machine Type: x86_64-pc-linux-gnu

Bash Version: 4.1 Patch Level: 5 Release Status: release

Description:
 I have two similiar scripts:
        #! /bin/bash
        pwd
        echo $_

        #! /bin/bash
        echo $_
        pwd

        The first one displays:
        /home/windriver/changes/NexS-235r1/with-camera
        pwd

        The second one displays:
        ./apply.sh
        /home/windriver/changes/NexS-235r1/with-camera


Repeat-By:
        See Description