I do have exactly the same problems as this guy ... with two different TARGUS ACP70EU ... so it seems that this could be a driver problem ...
Or could it be a problem with the firmware? Is there a tool to read out the firmware version? Or is there the possibilitiy for a downgrade of the firmware?
I get really mad about it ... sometimes it will work ... sometimes not ... a formely good part turns into a problem :-((