admin pages not found after server move

After moving my blogs to a new server, the login pages now return a 404 not found error. All the other pages and posts show up fine just no wp-login.php. I have 4 blogs on different domains and they all do the same except for 1 that is installed in the main directory. The others with the problems are all installed in sub-directories with the index page and blog directory set to display in the main directory. It seems obvious that the problem lies in these settings but I’m not sure how to fix it. Any ideas. Thanks kindly for your help.