Window Closes after login

[PAstEl]

I'm using a Windows 7 Ultimate right now and my problem is that right after I click the "login" button the fiesta window appears but only for a second then it closes and nothing...
So far i tried restarting my comp and uninstalled and installed *once fiesta but the same problem happened. Help would be greatly appreciated.

p.s. sorry for this, tried searching for similar topics but didn't know how to phrase it that well so all i got were irrelevant information.

Thanks in Advance