Dont try and make a mod unless you have mapped for several months or about a year at least. i tried, and failed and a few others here tried making a mod at a lower level too. and failed.
Ok, ant, you are very profound: penetrating or entering deeply into subjects of thought or knowledge; having deep insight or understanding: a profound thinker.
anyway, srry, my glasses are better then yours. and its NineTnine; as in: 99 not 1999
EDIT: anyway, you can still quote from a profound thinker
So i make a map with a couple of rooms, trigger etc, then i test it. Then i jump back into hammer and build onto it some more (brushes, triggers etc). i test it again and (sometimes) the new extentions i made are not there, only the stuff i had before. I reckon it just a leak, but i want to make sure, incase its something else.