404 Error -- Admin login.php not found

[TShooters]

This morning, when I try to go to my Admin login page, I get a 404 error.
FF tells me my login.php file is not found on the server. It is there.
I had made a backup of my files and db Sunday, and emptied my admin activity log after a prompt that it was 60 days old/full. Everything was working fine yesterday morning.

I uploaded the backup admin/login.php file this morning, but still no joy.
I downloaded my files again, and compared to Sunday's backup with WinMerge, and all files are identical. I have an email in to my host to ask if any changes to the server have been made, and awaiting his answer.

I've checked my db admin activity log and found nothing suspicious.

Other happenings:
My SSL cert expired Saturday, and I've put my store in showcase mode. I
followed the FAQ instructions on how to disable SSL. Anything else I should
have done?

Thanks in advance for any thoughts/recommendations!
Sharon

[TShooters]

Nevahmind...
Host says it's to do with the change from a dedicated IP address.