Your holding it wrong....oh wait i think i just made a huge
PR blunder.
I would guess you need to tell it you have read/write access.
I renamed everything via the adb shell (command line)
"androidsdk" directory is where ever you installed the sdk
C:\androidsdk\tools\adb shell
$su
#mount -o remount,rw -t yaffs2 /dev/block/mtdblock3 /system
#
#mv NewsWidget.apk NewsWidget.bak
#mv PhotoWidget.apk PhotoWidget.bak
#mv redding-7648-signed-zipped.apk redding-7648-signed-zipped.bak
#mv SocialMessaging.apk SocialMessaging.bak
shortened list of what i renamed.
the "mount" command is what i think your missing, before i did that i got he same error your seeing.
Their entries still sort of show up in the applications list. but they are not in the app drawer anymore. no kindle and etc.