To verify that it's
not a cookie issue in IE,
go to the Tools menu in IE, choose Internet Options, Privacy tab and click Advanced.
This time, check the override box, then change the First Party and Third Party options to Prompt.
Close the browser after making the changes and reopen it.
Go to
http://www.fellowshipdirectory.com and attempt to sign in.
You should get a prompt immediately after attempting to first access the site. If you allow the cookie at this time, you shouldn't be prompted again and your sign-in should be successful.
When I block the cookie, the sign-in isn't successful and I remain at the sign-in screen. You should have the same result.
(I'm working on duplicating your 'blank page' issue.)