Someone knows why??

[Anonymous]

Hello in autocad architecture 2012. A months ago a have a sheet with one viewport in perspective view and the others are floor plans and elevations OK? Then suddenly I open the sheet and the perspective view port become isometric so I put that in perspective view again and block the viewpor save the drawing closed and open again and the viewport again is in isometric view. I been trying everything I can image and still making the same behavior so anybody why or what I'm doing wrong.

I really appreciate your help if there is a solution.

Thank You 

[Anonymous]

It is really simple just save the drawing 2007 or higher and that's it. all the problem was because I was saving the drawings in 2004.