When I came back from my vacation last week, I found that I can no longer log on to the wp-admin of my site. I was freaked out at first and I thought the site got compromised or something. Google search did not find anything useful.
I finally contacted my hosting company, Blue Host, for support. They fixed my problem quickly. The culprit is the Supercache plugin. The plugin created rewrites on the .htaccess file. One of the rewrites caused the domain to redirect to a 404 error instead of loading the wp-admin page.
Earlier I had some issues with Blue Host’s support, but after this incident I am a loyal customer again.