Can you vent into the crawlspace or attic? You really need to get that hot air out of there, or consider flourescent lights.

Or try this: get a fan that is dedicated to blowing the space between your light and plants, and get a big ice block, set it in a big bowl and put it in front of the fan. Or just set a couple of ice blocks near your plants. They may last all day that way and decrease temps a few degrees. I've recently thought about trying something like this. I'll let you know how it works if I come up with something.