What graphics card do you have?
What is your OS?
What version/revision of Blender is crashing?

Graphics: I have an Intel Series 4 Chipset graphics device
OS - Windows 7 64bit SP1
Blender: 2.7 RC 2 (Sorry should have mentioned that :-D)

I've also tried regressing to the previous build 2.56a and this no longer works either, I have also tried the 32 bit versions of both versions and still no luck.
I've also tried removing everything to do with Blender from my machine as well now (all folders and registry keys) with no success.

I suspect something somewhere is corrupt when trying to open the preferences, when ran through VS debugger it is just coming up with an Access Violation. The only other thing it could be is that I recently applied Windows 7 SP1

Might try running processmon or debug view if I get time. Just very frusutrating as nothing seems to get me back to working.

Thanks for your help

It's a known issue... we have serious problems with intel-gfx cards opening a 2nd window in Blender.
This is not consistant for every windows version even, nor does it happen for intel gfx in OSX or Linux. Nvidia/ATI cards do fine in Windows.

Main problem is we need devs with this kind of low level knowledge to dive into it. It is probably something intel drivers do differently than the others... maybe we can discover the bypass (or bug) soon.

Moving to ogl tracker.

Moved from Blender 2.5 Bug Tracker to OpenGL errors

The odd thing I think about that comment is that it has worked before. I was playing arround with plugins and other options before I both upgraded to the latest RC and Win7 SP1 (I wich I had started and checked it after installing SP1 and before upgrading to see which caused it)

I've downloaded the latest SVN truck and will try to load it up and see where it breaks to see if I can offer anything.
Any tips welcome ;-)

Fixing my statement: it also happens in Linux...

I suspect it's not the same issue now, as i've resolved it in Windows (although it might help Linux, who knows).

What caused it to creak in the end was because I had switched to the Windows 7 Basic theme at some point in the past, disabling the Aero Theme, this must have turned off some crucial 3D component that Blender was depending on for opening a second window.

Reverted back to an Aero theme and it is working again now.

Odd case but it works. The rest of Blender was working fine (ish) without it though. If I get time (as I've downloaded the SVN anyway) I might try debugging it to see which specific call fails, but I wouldn't have thought it should matter since Blender works without Aero.

Thanks

Can close the issue, but probably needs some follow up or documentation update for the release

That's a good find! I'll ask others to check if this works...