When my other Admin goe's to login to ACP , all he gets is white screen. But I can get in fine?
Check Admin permissions and ask him to try from another borowser or device.
Also ask him to try refresh page... Ctrl+F5
He said he did all that and now when he tries all it doe's is redirect him to the index.
Have you checked admin permissions?
Have you put IP restrictions on the admin panel? He may have a dynamic IP and it may have changed.