The problem is simple : everytime i try to build the project, the loading bar get stuck at 100% and nothing happens next. If i Alt+Tab, i can’t go to the UnrealEd window anymore and i have to hard close the window. It’s quite annoying as i can’t do anything. The problem even occur when i’m building a raw project. I mean, i don’t change anything and the build bug the window aswell.
Can somebody help me ?? :o
Sorry for my bad english …
The build may take a while depending on how complex the level is. If there’s a lot of stuff or if your computer isn’t very powerful then it can go slow. Also, since it uses CPU power, it can slow down your computer while it builds. You can try changing the Lighting quality to Draft and that may help. Production quality is slower.
The lighting quality is set to “preview”, so it’s supposed to be the shorter option. The problem didn’t occur before, just one time it get bugged and then i can’t do anymore. And I don’t think the basic level with the two chairs is “complex” 
I’ve found that only the light build is bugged : geometry paths and LODs are ok. The bar freezes with the message “gathering level geometry”.
Ok, the problem disappeared by himself … Thank you anyway ^-^ I hope he won’t come up anymore.