Deinstalling 7Zip, installing WinRAR, deactivating Avira AntiVir doesn't change anything... I'll use the other computer!
Thank you nevertheless!

I tried it several times and on different PCs. (Another PC running Windows 7 created the same problem.)

At first I saved a plan containing only walls, closed the program and opened the file again.

As soon as I add to this same plan or a door or a window or a piece of furniture, I can't open this ...

Hello,
first of all thanks a lot for this great and powerful program!

I have a problem, opening saved files on a PC running Windows 7.

If the "*.sh3d" contains only walls and rooms, there is no problem.
If it contains windows or doors, the file can't be opened. The error message says "Can't open ...