Physical (USB) keyboard keeps waking Android ICS tablet from sleep
I now have the same issue using a 7" Sumvison Astro+ after updating the firmware to the manufactures latest ICS listed version. From what i can tell this issue has been introduced as it wasn't present when i first received the tablet with the original firmware.

The details the device lists are 

Android version 4.0.3 
build version 9F2-D1-H2-H01-2102.20120515
baseband version 1.1
Kernel version 3.0.8+

The release notes list nothing but stability improvements so no clues as to what has been tinkered with. Generally the update was successful a Wi-fi issue i had with streaming music has been cleared and the devices has had it's default CPU speed bumped up which makes it feel snappier, if this keyboard issue wasn't there it would be perfect.