Recently something happened to my tablet and it wouldn’t boot past the android skateboarder screen (never got to the eye). The /system/bin folder had been deleted, so I couldn’t get into the adb shell. I could get to adb and see the device, though. After pulling what little bit of hair I had left out, I finally found an UPDATE.ZIP file that restored everything.
Click the small blue download link (it took two tries to finish downloading this.
If the link goes down, let me know. I have a copy of the file.