After another check on windows update, another SP1 update got installed (cf my updates history: http://i.imgur.com/pckkJ6R.png . As you can see here: it's the same KB number, but different installation date).
Anyway, sorry about that but this fixed the issue actually.

I don't have any mod.
Do you want me to install the optimized script manually to check if it's better? I'd be happy to try.

Thanks.

The issue is still present after I installed the W7 SP1.
I'm not sure someone will read this reply as it's in the "not a bug" forum, but in case, here is an imgur album with the requested screenshots:

http://imgur.com/a/D1huS

Script Update times goes from 0.17 to 21.8.

I have another computer running Ubuntu 14.04 32b which has similar CPU but slower graphics card. There is no issue there.

Hope this helps.

I played the game using the demo without issues. I purchased the full version and started the campaing New Hope. Everything works fine, until I place the first item of the game: the lab. Here the game slows down so much it's nearly unplayable. As long as I don't place the lab, game is running fine. ...