also, when opening the membercard, it shows a small black bg-image (or whatever it is) of the membercard popping up before opening up the membercard.
The same when closing the membercard, it does not close immediately, but a small membercard-bg-image (without content) is showing before the membercard gets finally closed.
That's really weird. I'm running Windows XP SP3 at the moment and Firefox 3.6.8, and I can't reproduce any of your problems. I've been going through clicking everything every which way to try and reproduce this and I can't.
In that last screenshot, the graphics seem like you are only using 16bit mode instead of 32bit. Really seems to be a issue with your graphics/card or something. Check and make sure the display is set to 32bit mode.