Sometimes when I have Firefox open while I also have Blender open, Firefox will go black and I cannot interact with it. The only way to fix this is to close Firefox or Blender and start it up again.
I also cannot open multiple instances of Blender. The second one will not show any icons and sections will turn black when the splash screen is gone.
No icons when the splash is there(splash didn’t show up in screenshot):
Sections turn black when splash is gone:
I’m running on Windows XP. This never happened to me with 2.65, only when I got 2.66.