Problems in autocad 2012 when opening files from autocad 2011 saved as 2000

I had a problem here with some files.
We worked using AutoCAD 2011 and, as our partners generally don't use this version, we usually save our files as 2000.
Now, we have upgraded some machines to Autocad 2012 and some files (I can't say how much of then), when opened at 2012 version, presented some hatches, or blocks (lots of this) in the drawing. It seems to be some dirty elements. And the same file, opened again at 2011 version, does not present this.
I don't know what is happenig and neither how to resolv this. I tried to execute the comand Overkill at 2012 version and it doesn't worked. But at 2011 version, it resolved.
For me, it's a problem with the software (and it persists at 2013 version). Anyone had the same problem? or could Help me?
I have more than 1Tb in files that can present this trouble...
Thanks a lot!

Would you be able to post one of the offending files? I'll have a peek on Monday.......

Tks, wolfgrrlone,
I'm sendind the file. It seems to be that the hatchs was elements inside block (that in this drawing are exploded, unfortunately) I have more examples in my office but I'll be there only on monday.
A technician tell me that the problems are in the file, but for me it's too strange that it only apears in 2012 and 2013 version. And i'm worried about the other files from my office...
If you need more information, please, tell me. Tks again

Attachment 85796

Try this version.
I opened it in 2010, used the Select command and windowed everything visible, zoomed out (0.1x) and Erased All (remove) Previous. Then opened it in 2013 where it looked okay.

Previous multiple purging made no difference.
As for an explanation - no idea. :(

It worked here, at 2012 version. but, I didn't understand what have you done.
As i said before, I solved this using the comand overkill. And It seems to be that saving the file as 2010 version solves the problem to (but we have to do this with the Autocad 2010 or the Viewer (not automatically)

But my problem is just that I'm trying to find a reason. Because we don't have 2010 or 2011 version. As we have subscription, we installed the 2012 version and, because of the problem, tested the 2013 one end it doens't worked too.
I'm trying to find what is happenig and if it's happening with anyone else, 'cause i think autodesk could solve this. But it's out of my hands. I'm in Brasil and trying to make contact with them here. But for instance, they don't know what is happening.

May i ask you to help me on this? The quick solution I think we have. But I'm trying to find the big one...

Tks

I've explained what I did but I have no idea why it worked, or rather, what caused the problem. :(

I know it's just a workaround, not a fix.

This is definitely strange.

I can't give a reason why it is happening either. You say that you are on subscription, so that means that you would have maintenance support as well. I'd give this one to Autodesk to try and figure out. I think at this point it may be your best bet.

I played around with this a bit more and chose the "Flatten" command just to see what would happen. It changed the hatching to "symbols", of a sort. I've posted a screenshot of what happened to the file as well as attached it here. This is in 2012.

Attachment 85799

Jaberwork. I undestood this. Tks a lot for the help.

Wolfgrrone, with the flatten, the problem apears in 2011 too :-)
For me, its seams to be that the objects was something like surfaces and with the flatten command it was converted to triangular lines... Could be?

That's true. I have the subscription and maintenance support as well. The problem is that autodesk and the autorized Sailor is telling me that the problem are in my files. I have not too much knowledgements in TI, but the ones I have are enought to made me believe that the problem are not on the files... Or, If are on this, that the program made this... Sometime.
I'm just trying to find another experiences to have some knowledgements to talk with the people from Autodesk... I'm calling them for a meeting. Let's see what they say... Tks a lot. If you know anything else that could help me I woud be grateful.

If I have any answer or position, I'll post it here ;-)

Could these files have been created or edited with non-autocad software?

In wolfgrrlone's file, all the unwanted hatch entities have changed to lwpolylines. :screwy: