Are you sure you're not running it in multiplayer?
Launch HL, then hit the little key below Esc and type "map yourmapname". That will start your map in single-player. If you still don't see monsters then something very odd is wrong.
Hm, well, as far as I know it doesn't yet provide the recommended daily allowance of vitamin E, although I think that will likely be included with atom's new work
I don't usually bother about that, since people who don't know what they're talking about say it badly. I give 'em the right answer, better-written, and hey.