localhost games do not work

[bartvbl]

When I open a game/replay, which is hosted on my own pc, the large fullscrfeen spring window comes up for a fraction of a second, and then turns into a smaller window, that just remains black. No matter how long I wait, nothing comes up. For some strange reason everything works fine when I join an online game, which is not hosted on my own pc. Does anyone else got problems with this?

EDIT: reinstall works fine for 1 game, then it doesnt work again anymore
Here is an infolog of an occasion where this occurs:
http://pastebin.com/m44ccd36b