I held F3 + C for 2 minutes exactly.
No crash, I had to close it through Task Manager again.
Another thing, 1.4.5 and other versions have stopped working. I am beginning to think it might be a problem with my graphics card, since Minecraft and other OpenGL applications are strangely running very slow.
I had the same problem.
The problem came after I updated my video drivers. Turns out that the nVidia drivers I installed were buggy, I just uninstalled them then reinstalled the drivers that came with my video card.
So either try updating your video drivers, or downgrading.