I have a 5600 with a Targus keyboard and OZ 3.5.4.  I installed irk-targus, and it worked great.  But a little later, something hanged, and after I rebooted, I could not get irk-targus to work anymore.  I removed and reinstalled the package, but it still doesn't work.  I killed irattach and still couldn't get it working.  Any hints?  Thanks.