geometry is hidden in viewport until selected.

I didn't have this issue in 14 but in 15 I cant seem to see any geometry unless they are selected. I can't find anything in the display menu but I'm obviously missing something, any ideas?
Thanks.

It could be that you hit the Y key with the mouse in the viewport and saved your Desktop with this setting.
The visibility menu is on the viewport top toolbar. See attached pic.

(and welcome to the vfx mountain!)

It sounds like your driver could be failing to compile the GLSL shader responsible for smooth shading. You can set the environment variable HOUDINI_OGL_DUMP_SHADER_ERRORS to 1 to see if there are GLSL compile errors.

Another common issue is Alpha being set to 0. In this case, selecting the object will show you the wireframe but the surface will remain completely transparent. You can either delete the Alpha attribute that's causing the problem, or look at the material and see if OGL Alpha is set to 0.

Thanks Guillaume,
That fixed it. You are probably correct as to how my clumsy stumbling caused this.
Looking forward the climb to the top of this VFX mountain for sure!

Thanks Twod too, although your answer actually terrified me.

Yeah, the fact that the GLSL compiler is part of the driver on a user's system has always been pretty terrifying to me

Luckily the OpenGL ARB has recognized this as pretty important issue to solve.