Command not allowed because drawing contains objects from a newer version of this app

AutoCAD Architecture 2008

So this one has got me stumped.

I start a new drawing from a template file that I have customized for me

I add some objects (box, Sphere, et. al.)

Then I try and use the "Hide Objects" tool and I get the error message "Command not allowed because drawing contains objects from a newer version of this app."

If I close the drawing and start a new drawing again but this time I use the "canned" acad.dwt template, the command works.

So there is obviously, or at least to me, something amiss with my template file. Right? Any idea how to get my template file so that it will work? I've tried re-opening the template file as a template and re-saving it, but that didn't help. When I open my template file for editing, the command window spits the following out:

Opening an AutoCAD 2007 format file.
Regenerating model.
Press ENTER to continue:
AutoCAD menu utilities loaded.
AutoCAD Architecture menu utilities loaded.

Autodesk DWG.  This file is a TrustedDWG last saved by an Autodesk application 
or Autodesk licensed application.

Any suggestions?

I should mention that I also have AutoCAD MEP 2011 install on the same machine if that make any difference. I don't use it because I can't draw with that #@$% ribbon...

Thanks,

Chuck