Site Hacked?

My site has gone down twice this weekend. When I fixed it yesterday I thought it was a DB issue. It went down again today and when I checked the logs I saw some strange referring URLs. All of them were from WordPress sites and looked like this http://www.example.com/wp-login.php. There are about 20 different domains all with the /wp-login.php. I am not sure if it was hacked, but those URLs are pointing me in that direction.

Has anybody else seen this?