i can hear sounds, no error shows up.
i am in the level, but there's just nothing there.
sometimes it appears some parts of the level, but only for little seconds, and it desappears after.
This is a bizarre occurrence. With no error messages or anything, it makes it very hard to diagnose what's going on. What specs are your PC out of interest?
my pc is a windows 7 ultimate service 1 and it is 64 bit.