This is a recent problem.
In some dwgs, CtrlC/Copybase/wblock fails unless * (the entire drawing) is selected. That is, none of these actions succeed for a selection set -- any entity, even a simple text entity. This is happening using AutoCAD 2000 (file saved from 06 to 2000) The commands work fine when the 2000 dwg is opened using AutoCAD 2006, but not when the 2000 dwg is opend using AutoCAD 2000. (Perhaps AutoDesk has done something deliberately?)
We have 2000 and 2006. If the same dwg is opened in 2006 the commands work normally. As mentioned above, this is a newly observed problem. We used to use another CAD program to save 2004=2005=2006 dwgs to 2000 dwgs It seems that this problem started when we started using 2006 to saveas 2000. I would prefer, and am trying to persuade more licences for 2007 rather than the other CAD program -- but this problem is not helping.
Has anyone else had this problem? (It is SIMILAR description to the saving 2007 to 2000 problems/threads but seems to be different in that the 2007 problem seems to effects any other version; we are not using 2007; I can't know if the files I am getting were once 07 saved to 04=05=06 but the 07 described problem seems to say that if that were the case then WBLOCK, etc. would not work in 06 either, but it is working in 06 just not in 2000 from a file saved as 2000.