Sorry me but i don't know how open a map (like that of Matrix Reloaded.pk3) with JKRadiant forc hange some texture. Please help me!!TANKSS;)
You can only open .map files i'm affraid not bsp files and pk3's have the .bsp file inside.
You would need a converter which is what i want a converter to convert bsp's to maps.
To open pk3's you need something like packscape or do it the easy way and rename it to .zip
Try here for tips: http://www.mappersguild.com/