Sounds like you flashed the downgrade image. See post #3 of the Windows sticky I started; that's the process you should follow to unroot. You can adapt the same procedure to Mac. Just put a ./ in front of the ADB commands.
Cory - I was trying to return to stock as well tonight following the procedure but as you noted for the MAC. I got to the last part
# dd if=/data/local/misc.img of=/dev/block/mmcblk0p17
and I get a denied error. Here is the commands I typed into the terminal.
$ cd ..
$ cd ..
$ cd and*
$ cd tools
$ ./adb devices ( the device comes up as attached)
$ ./adb push misc.img /data/local/
$ ./adb push busybox /data/local/
$ ./adb shell chmod 777 /data/local/busybox
$ ./adb shell
Then type the following; not including the $
$ su (when I typed this I get permission denied and cannot proceed)
Then type the following; not including the #
# /data/local/busybox md5sum /data/local/misc.img
The Command window must display the following checksum: c88dd947eb3b36eec90503a3525ae0de
# dd if=/data/local/misc.img of=/dev/block/mmcblk0p17
# reboot bootloader
Any suggestions or corrections are greatly appreciated.