Complications with Tags

I am making a map, just made a beta, however I just went into a dilemma...

Every time I try to place a tag, it says:

"TagNameAndLocation" is not a valid tag

This does not make any sense, has anyone ever had this error?

Try to place a tag where, with what?

I was populating the map with sapian, and wanted to have weapons, and that error came up. tried to add vehicles, didnt work either

You need to be more specific... we can't tell what you're doing wrong/what Sapien's screwing up with unless you tell us as much as possible.

Basically he just went into Sapien, went to netgame equip like normal, tried to place a weapon/vehicle and it crashed giving him that error. I don't know man, back up your map (copy and paste scenario, bsp, lightmaps, and custom shaders) to a different folder, outside of map editor, and try reinstalling map editor.

I tried replacing the tags with the tags provided by TheGhost (see topic Halo 2 Tag Base) and it still did not work. This is starting to get annoying...