So, the “imagemaster” something like this, right? http://toys4techies.com/product_info.php?products_id=91&osCsid=0360c213420ed585e50f0f8a74268ad9

Did you sysprep the machines before doing a clone? There’s some info about prepping a machine with avast before imaging here: http://forum.avast.com/index.php?topic=45576.0

Also, to make sure that avast is completely removed, you should use the standard add/remove programs, then use the avast uninstall utility http://www.avast.com/uninstall-utility