I am a n00b mapper...just doing my first one.

Basically, ive made 3 rooms, linked together with craved entrances, and all is good i can run it in hl.exe and run around....very exciting indeed.

BUT I wanna obviously expand it etc...But wen i try and put another room on....It doesnt run anymore in hl.exe...it starts to run, but then freezes &ives me an error report thingy. Ive played around and made a small box outside the others, and it will run, then i made the box bigger..and it ran!!! THEN i hollowed the box out, and it did the freeze thing.

Any ideas!??? It cant be memory or anything, I have a 2Ghz p4, 512 ram, geoforce etc etc....