OpenGL runs in Software Mode? Nsight crashes, gDebugger finds no OpenGL calls.

Hi,
I am working on a small personal project involving OpenGL for rendering. In the beginning I was using Qt 4.8 which worked fine so far, except that I was unable to use NSight 3.0rc2 which just did nothing (it started and after some times stopped again without anything happened).
With gDebugger is was able to do some debugging, but in the OGL performance meter there was always 0 and the CPU load was quite heavy.

If I enabled OGLE in gDebugger I got some error messages - at the initialization and then the whole time the output is this:

OGLE: Category: 0x00000001, MessageID: 0x00800001
      A provided enum value is not accepted by this operation:  <pname>
      requires feature(s) disabled in the current profile.

And this:

OGLE: Category: 0x00000001, MessageID: 0x00800001
      A provided enum value is not accepted by this operation:  <pname>
      enum is invalid; expected GL_TEXTURE_ENV_MODE,
      GL_TEXTURE_ENV_COLOR, GL_COMBINE_RGB, GL_COMBINE_ALPHA,
      GL_SRC0_RGB, GL_SRC1_RGB, GL_SRC2_RGB, etc. (15 others).

After the first redraw of the window additionally this appears:

OGLE: Category: 0x00000002, MessageID: 0x0081000C
      Software rendering has been enabled because the current texture
      related state is not supported with the current hardware
      configuration:  Texture 0 is base level inconsistent. Check
      texture size.

The last message gave me a clue that maybe the whole thing just runs in software mode. In my Qt program i get 40fps in which is not very much drawn at the moment (maybe 5 cubes and a sphere with textures and some phong lighting).

My next step was to see if this was Qt related. After compiling 5.0 from source using -opengl desktop switch the problem was still there (or the error message changed a bit).

OGLE: Category: 0x00000001, MessageID: 0x00800001
      A provided enum value is not accepted by this operation:  <pname>
      operation is invalid because a required extension (OpenGL_3_1) is
      not supported.

The context had 3.1 (at least the request got answered like this from Qt).

My next step was to exclude Qt, so I started an empty project in Visual Studio 2010 with GLFW. I just copied the example code from here http://www.glfw.org/documentation.html into the main.cpp, set libs (opengl32.lib, GLFW.lib) and include and added an glClear(GL_COLOR_BUFFER_BIT) in the loop.

Nsight now crashes with an white GLFW window, gDebugger stops showing something on the OGL performance meter as soon as I set the requested OpenGL version to something like 3.2 or 4.0 which I’d like to use.

Platform is Windows 8, using Visual Studio 2010 on a GeForce 660Ti with the newest driver (same problems existed some driver versions before, I just updated today). I am stuck here now for several days, unable to find a solution.