One of the admins of a site we are maintaining is unable to log into the CP after i upgraded EE to 2.5.3
What I am seeing in the acces logs, is that before, she always (succesfully) logged in from the ip address 0.0.0.0. I guess she still tries to log in from this ip now, but EE blocks this.
Is there something I can do, or is the issue caused by her local situation?
If you go to Admin ➔ Security & Privacy ➔ Security & Sessions have you got 'require IP address' enabled? If so, disabling that should do the trick.
That said, rather than disabling security features, you would likely be better off looking into why her IP address is not being detected. The underlying problem is probably a local one rather than an issue with EE.