I hadn't set it up the way yours is, so I've changed that. It didn't make a difference, actually, until I re-installed the editor. Everything seems to be working now! Thank you both for the help, I really appreciate it.
I will also give GtkRadiant a try.

I have already extracted the .pk3 files. Unless I'm missing something right in front of my face, the FAQ only explains that .pk3 files must be extracted, and not how to load the textures into the editor afterwords, so this is where I'm stuck.

J.A.C.K. supports all three Quake games, including others. It includes FGD files and build programs for them. The only problem is trying to figure out how to configure it for Quake III.
http://jack.hlfx.ru/en/

Hello. I'm hoping somebody here is familiar with J.A.C.K., a Half-Life and Quake map editor. I'm having some difficulties configuring it for Quake III mapping. For instance, it asks for a .wad file for textures, but I have not found a .wad file for Quake III in any of it's .pak3 files. If anyone kno...