The main URL changes when I try to log in on wp-admin

Hi,

I have done a mistake in two of my domenes, and somehow linked them together.
I have two pages: http://www.example1.com and http://www.example2.com.

When I go to http://www.example1.com/wp-admin, it changes to http://www.example2.com/wp-admin, and none of the two password is working. It suggest that I go back to http://www.example1.com, and askes if I´m lost.

Any solutions?

Thanks