Display issue

[Bob106]

Hi everyone
Sorry for my terrible english   
I have a display issue, really annonying when i scroll the game, pixelisation's coming.
The strange thing is that only happens on the second time, the first play after the installation is fine (32 or 64 bits, I didn't use steam). No mods, just vanilla.
Somebody knows why it's happening and how I can fix it ?
Thank you !