HaloMods "Classic" Read-only Archive

i made a random attempt to mod halo 1 so i open up dothalo (i hear its compatible with halo 1 maps) and the tags come up like normal, but every time i try to edit any tag, it gives me the little error window and makes me close the map and corrupts it. am i doing something wrong or do i just need a plugin?

post a picture of the error so people can actually help

Please don't bump.