Step7 NetPro -opening project problem

I have a problem and i can't resolve it.

I want to configure some connection beetween plc's,hmi's etc but whenever I try tu run the NetPro using icon in toolbar or net icon in Simatic Menager [MPI(1), Ethernet(1), Profibus(1)] i get the message:

Network open (2263:9)
Unable to project 'xyz'
Another application might be processing it.

Of course the all the project files are closed.

Another symptomps:

1. If I try to run the "Connections" from the CPU panel i get the same message but with the next:

Open Object (256:26)
An OLE error occured.

2. When I try to open the properties tab of the existing network's they open only in "read only" mode.

Any ideas? All the methods with use of "reorganization" failed.

I would try to repair the STEP7 installation.

Ok. I'll try. But other strange thing is that, that on another computer with STEP7 the messages are the same. So I think it's problem within my project.

Try to post your project here as archived zip.

Jesper: I reinstalled the S7 and all still no effect
Here is the project http://www.ee.pw.edu.pl/~hanczurp/Xplctalk.zip (7MB)

Madman: Thanks, but I've already found it and checked this hints.

I got the same error.
I managed to clear the error by creating an empty STEP7 project, then simply copy-paste everything in the Simatic Manager from the defective project to the new (all stations and all networks).

Thank you very much. I'll try to do the same.
BTW, quite easy remedy

It really worked well. Just ctrl-n,ctrl-c,ctrl-v and all your problems are gone. Magic!
Thanks a lot once more time!