Hey everyone. I did read the article on the codex about logging in.
The site is on HostGator, along with about 75 other WP sites that have had no known instance of having problems logging in.
Only the client, both at her work location and at her home location on two different computers, can not login.
At first she was able to login. Then I made a change in the config file to limit the number of revisions saved. After that she could not login. I deleted the line in the config file, and she still could not login. She told me she was getting a cookie error.
I sent her instructions on how to clear her browser history and cookies on both IE (version 8) and FF (version unknown). I asked her to try both browsers.
Next I totally killed both the config and the .htaccess files and let WP regenerate new files. She still can not login.
Next I killed her personal user account and created a brand new account with a very simple username and password and sent instructions on it being case sensitive, please check your cap locks etc. She still could not login.
In the meanwhile I tested the login on a lap top running IE 6 and had someone outside of my office login with out any problem using both her account and my account.
I also had her try to login to my personal WP site (on the same server) and she was able to.
Next thing I did was set up her entire website on a different domain but on the same server. She was then able to login on the new domain using the new user account I set up for her.
I then suspected she had something cached but then wondered "on two different computers in their office?!?".
Then I get into the office this morning and she sends me an email stating she tried to work on it from home on her laptop, then on her home desktop and she could not get logged in to either version of the website (both the original domain and the new domain).
The theme is a modified 2010. I have not changed the theme, since I knew there are people who can login.
Does anyone have any ideas?