In my experience a "key not found" error generally refers to something missing ... a layer, linetype, shape or some other innocuous item that is hard to pinpoint.
Try running the routine from your installation of 2006, but using the drawing he says works in 2006, but does not work in 2008.
Something I have seen employees at some places do is make the program find a file on a network share. If that file no longer exists, meaning the company removed it from the system because the employee is no longer there or the ex-employee removed it when he left, the routine cannot find it, thus cannot continue.