So the problem exists in php5.3 and 5.4 but not 5.2. I was hoping 7.5.8 would fix the problem. Looks like I'm wrong.
No problems with the current version of Chrome or Firefox logging in when the server is running php 5.2, 5.3 and probably 5.4 and 5.5.
But, as you've mentioned, users of Internet Explorer 8 will probably have log in issues if the server is running php 5.3 (confirmed) or 5.4 or 5.5.
