Users I setup in WordPress can't log in…

I’m having problems with users I setup in WordPress being able to log in from different IP addresses, other than my own. I was alerted to this issue when I setup a guest blogger through admin panel. I tested my guest bloggers login details and was able to access the dashboard. However, my guest blogger gets a 404 page – no dashboard. I tested the login data again, no problem.

I then had my host (HostGator) try and log in as a test user I set up and they also rec’d 404. I replicated the 404 error by hiding my IP address and I get the 404, even as admin. My wife tried to log in from her office as the test user, same 404.

Bottom line, apparently my IP address is the only IP address that allows logins. Any other IP address WP partially logs a user in, by that I mean you can see the admin toolbar but get the 404 page, no dashboard. Any suggestions, tips?