I had similar issues to this when playing Portal 2 a few months ago. Turned out my graphics card was massively overheating and turning itself off to prevent meltdown. Trying using something like http://www.ozone3d.net/benchmarks/fur to stress your card, and http://www.cpuid.com/softwares/hwmonitor.h...

Try changing view using the numpad keys, rather than the "change view" button, which doesn't really seem to work properly.