...also experiencing this same problem. I'm also having trouble inserting blocks. I am not enjoying my 2009 software at all.
I called my re-seller tech support about this. It's a compatability issue. If the drawing has been opened with 2010, they will need to export to autocad before someone with 2009 can open it. They said as long as you're moving files forward there should be no problems, autocad takes care of the change for you.
I know this is an old thread, but I'm having this same problem in ACAD 2010. I'm saving as 2007 and when I PASTECLIP I get *invalid*. I don't have 2009 at all, only 2010, and I'm working in files that have never been opened in another version of CAD.
You may be pasting an AEC or 2010 object that's not allowed in 2007's format (reason you can do it in R2009 is it only has 2007 as a format).
Opening a file in 2010, regardless of your SAVE setting, will upgrade AEC content to a format not accessible in R2009 or lower. AECTOACAD command may fix all of your files.
I have had a same problem.
In my perception it happanes while we try to copy object which is created by Other CAD softwares(Or custom made objects,such as hatch from Ravit). I delete costom made hatches before I copy with the base point. It worked for me.