I am wondering if that might be the first piece of advice to anyone having trouble with Hammer or ZHLT. Reinstall, somene else had problems that were solved with a reinstall of Hammer.
Also, make sure you have the latest .fgd file, the latest ones come with all the good stuff for ZHLT light effects. I think the most recent HL one is half-life_3x.fgd. DoD has just released a new .fgd, cool stuff in that one, like snow.
Anyway glad you fixed it, sorry about the register thing, It's just that your name didn't highlight, and I was too lazy to check the user list.